It mostly depends on your budget. Under $2k gets you a pretty solid self tuning throttle body fuel injection and timing control, but if you want to go multi port, it’s going to cost more.
The self tuning throttle body kits are becoming popular options even for the stock land cruiser motor. I have a Holley sniper on mine and love it. But there are several brands and models to choose from. Get on you tube and check out some reviews and some of the initial startups
I just finished (Mar 19') installing a FiTech (Base model 400 hp) model onto a 70's Chevy 350 in my 40. Started right up, been driving it as much as I can without a single issue (So far). I'm very in-experienced at electrical, so if I can do it, anyone can. PM me in you would like more info. ***Disclaimer*** - I also installed a new fuel tank, sender, Aeromotive in-tank fuel pump, new hoses, filter, wiring, etc before I started the Fi-Tech. I wanted to start the EFI install with a solid Fuel system first. (This is important and required the most research).
I installed a Holley Stealth Ram MPFI system on my 383. The actual installation was not hard. I downloaded a preset program for my application and several others but none of the Holley programs ran correctly. It would have taken a good amount of learning to get the program right on my own. I was short on time so took it to a shop to have them tune it. They had to adjust all the Holley preset program values and cancel out the wideband O2 sensor to get it running correctly.
The stealth ram set up is certainly capable of more than I need for my use, I think a tbi set up would have been fine for my needs.
I am happy with how it runs now but if I had it to do over again I would go with a newer tbi system. The stealth ram was expensive, and required a knowledgeable shop to complete the install. Tbi would have cost less and from what I have read about install is sounds simpler and more plug and play like.
The decision point for EFI depends on a couple, external factors.
1) how experienced is the installer and user
2) how non-stock the motor is that it is supposed to fuel.
I've said time and again, that the best tuners are ones who can tune a carburetor. The motor itself doesn't care how it gets spark, fuel, and air - but it does care if it is getting the right amounts of each. Carbs are more straightforward because they are analog - there's an idle circuit, an enrichment circuit, and a metering circuit. EFI has all of those things but can do so in different ways - if you don't know the basics of why an engine runs well (or not) with a carb.... EFI will kill you. Add to this, if you can read a spark plug, you're miles ahead. The EFI system is supposed to check barometric pressure, air density, temperature, and check how it's doing with the O2 system - way too often, people come to mechanics to solve 'problems with that junk EFI' that are due to a sensor reading incorrectly.
Caveats said.... my non-inclusive list of EFI systems and ease of use. All I've used, tuned, or thrown away because they were junk.
EZ-EFI, Holley Atomic - is the simplest.... bolt on the throttle body, no tank holes, just a couple wires and boom, you're efi'ing. No spark control, very robust maps... perfect for the stock motor. And there is its problem. If you motor is more then 10% higher in output, the EZ EFI is going to be trouble. It takes your tuning inputs as advice to ignore. There are no fuel maps to adjust. I seriously believe that the only reason they have the 'input' for changing the tables is to make the person feel like they tuned their motor.... that said, you have a stock motor and it's really a good deal... but it also has no spark control - which is good and bad. Personally, I'm not a fan of EZ-EFI. Another way to judge.... is the motor stock? yes, then these types of systems.... their limit, though, is 400 hp.
FI-tech/Holley Sniper EFI (that use throttle bodies) - both of these are a bit more robust in that there is boost control and fuel tables that can be tuned. To the beginner, know what you're doing because here be dragons. If you mess up with spark control (e.g. you don't understand how advance works and why), you could literally melt down your motor. Hp limit is roughly 700 hp or power adder.
DIYtunes (megasquirt), Holley Dominator, Haltech, These are systems that will do whatever you tell them to do when you tell them to do it. They can control multiple injectors, coils, don't care what crank sensor, you can use them to control nitrous, boost, heck, even radio volume (so you don't lose that sweet, turbo noise) you use just so long as you program it correctly. These land bricked cars in the shop pretty often. Even if you do get it all right, you're still paying someone with a dyno to fine tune. With that said, anything north of about 700 hp needs the control these give.
The OEMs (by this I mean, GM and Bosch), have hundreds of engineers whose job is to tune, refine, and design EFI systems. Companies (like Howells) have done a reasonable job of helping these systems adapt to non-stock use; but they make decisions that may or may not be something you want or need. While you must eliminate the anti-theft devices on the stock stuff, there are things - e.g. the speed input on TBI, which, depending on the installer, may or may not be something they wish to retain. Old OEM - such as 90s TBI, struggle with cam changes and demand a reburned chip to control them. This is pretty cool if you're building a truck to drive from Alaska to Chile because you'll never be more then a few hundred miles from any place that has parts. Not just that but these systems are robust and capable of handling the deserts of Chile to the floor of Death Valley without any input from the programmer. Newer OEM (e.g. LS motors) have been thoroughly cracked by the aftermarket and can handle if, once you get to the mountains of Chile, you decide to bolt a turbo on to handle the mountain passes (10,000 feet or more). A properly done OEM system is better then most aftermarket.... unless you want more, then OEM quickly falls away.
I feel the need to step back. There are a couple of levels of EFI.
1. The most basic has been mentioned. Bolt on a throttle body injection and tune it up using whatever tools you have at hand. These are simple and easy and get you the reliability of EFI.
2. The next level, that I suggest is a good idea, is an EFI that takes O2 sensor input and either a MAP or MAF. These systems are self tuning (once you get them set up) and the odds of melting down your engine are significantly reduced and they will ususally tell you if there's something wrong. You can also fine tune them to maximize mileage or horsepower.
3. The next level is one that takes over ignition timing. This means the computer is handling timing advance on the fly - dynamically. This really allows you to fine tune an engine. But, it's also really complicated on an engine like yours and I don't think it's worth the effort. If you have a points distributor, upgrade it to electronic ignition and call it good.
I cant' help responding to the carburetor comment. Carburetors are in tune for about day after they are set up. Then, changing barometric pressure, changing altitude, changing weather, and time all contribute to moving it out tune. Add a vacuum advance distributor and the thing is very rarely in perfect tune.
The big advantage of an EFI system with O2 sensors and MAP or MAF is that it's self tuning. It's always running near stoich, already running clean, always getting near the best mileage, plugs aren't getting fouled, etc.
Once you go EFI with O2 and MAP or MAF, then you stop thinking like a carburetor and start thinking of the engine as an air pump - which is what an engine is. Once you get into that head space, then tuning is very different. It's all about airflow. You don't tune and EFI system like a carburetor with an injector. It's totally different way of looking at it. A carburetor is a remarkable piece of equipment. But, it's an artifact of last century.