I gave my 80 to my son and i got a gx470. I suppose it all depends on what kinda trails you want to do.
My 80 had a basic OME 2” lift with 33” tires and armor.
I did the same on the gx470 with 33” tires, 2” lift using the air bag trick, and skid plates and rock sliders.
I still think the 80 articulates better and has more crawling capability, but the gx470 has more horses, is more nimble, and is way more comfortable. I need to do the rear coil conversion on gx470 with improved rear links to get the rear to articulate better and improve traction. That’s one mans opinion.
If you really want to go low cost, just get 32”x10” all terrain tires on the stock allows and remove the running boards. You can do all the fireRoads and some easy/medium trails with that.
The beauty of the GX - it's capable as heck in stock form, can easily be made better, too.
If you want bigger tires, note that the wheel wells are pretty tight, even with lift, you will have to trim, especially if wheel travel is stock (i.e., most all spring lifts still utilize the stock travel).
I have had mine a little over a year. I did 2" suspension lift with airbag delete, Dobinson's springs and shocks all around. I have 33"s. I got the wheels and tires clearing pretty well, so there's no rubbing on day to day driving. Under hard articulation, the fronts will rub no matter what you do. I have wheeled it in a lot of pretty tough trails, but I do think I could have wheeled almost all of them in stock form, too. It amazes me what it can do without lockers. As you know, though - lockers can be a game changer, but they are spendy. So do it only if you need to do it to accomplish a goal.
The thing I like about the setup I have is that it rides super compliant on road and off - the slightly taller wheel absorbs bumps a bit better than factory size. This makes it nice on road and off, and the Dobinson's springs are well tuned to your need (they have mutliple weights available, depending on what you're looking for).
So yes - to echo what everyone else says: How do you plan to use it? What's the goal? Start there and work your way backwards.
The traction control on GX is pretry good off road. If you familiar with locking diff they always slide to the low side in slippery condition. The traction control have much less tendency to do that. The A-Trac although will halt forward progress a bit until it figure out which wheel have traction would still move the truck forward as long as the wheel on the ground have enough traction.
2-3" of lift is most common. My personal preference 2" lift is better for standard travel suspension. 3" is better reserved for long travel. Max the front caster to get the most clearance for the front wheel from hitting the body mount. Also highly recommended to trim front and rear bumper to minimize trail damage if you do not have steel bumper.
I run 255 80 17 and don't have any rub after moving the fender liner forward a bit. Many times my truck surprised people with its performance off road because it look so stock.