*Long Post Warning*
Woah thats a pretty big question with a looooooooot of conflicting opinions.
Heres what I think, you may want to chime in with some specifics of your current cruiser condition, what you plan to do with it, shop, wrenching ability....etc...etc...etc
When I first bought my Cruiser my initial intention was to get it into Daily Driver condition (remember DD condition for me is considerably less than most, I have a ~1 mile roud trip daily). Once I accomplished this, I started to dream and plan about upgrades.
Originally I planned on dropping in a Chevy, parts availability and mmmm power were beckoning. I then realized that my cruiser would be down for waay longer than I wanted, and that I really liked the F engine, and wanted to keep things as original as possible. Almost went for a 2.5" lift, ended up with a 4", realized the pros of the 4" outweighed the cons (are there any ???.)
Here's my abbreviated conclusion:
I am a 1/2 restorer 1/2 off road modifier. I want the most I can get off road out of my cruiser, without losing that classic cruiser feel. I also found that many of the upgrades people rave about only seem like so much of an upgrade because their original equipment was worn out. Replace/repair the original first (unless its prohibitevly expensive) and see if you still want to upgrade. Hence, I concentrate on restoring the general condition of my cruiser, while infusing off road mods. Ie. instead of replacing my worn out suspension with new oem springs, I opted for a 4" lift. A good friend of mine purchased a '78 with a meticulous nearly perfect frame-up resto done, and it is a joy to drive on the road, and really makes you feel like you are test driving a new cruiser back in '78. It pains me to hear him talk about lifting it and cutting out fenders when its been so meticulously restored. Its a double edged sword, restore to factory specs, won't perform as well offroad, might cost a little more in the long run, do all the popular upgrades, lose some of that cruiser feel, I mean come on I know I can't outsmart the Toyota engineers. My favorite route is to upgrade using later Toyota cruiser parts, ie disc brakes, 2f 4 spd in a F engined cruiser. Let us know what you want to do with it, and you will get more specific advice. By the way, welcome, you'll find lotsa good advice and a few good laughs here too.
*Long Post Warning over*