That's beautiful! It looks a lot like the one a wheeling buddy of mine drove--only nicer. I agree--I would change as little as possible on it and just focus on the mechanical aspects. It'd even be a shame to swap out those SR5 wheels. They reflect the time period so well and they clean up really nicely with some balled-up aluminum foil and water. I have those same wheels on my '85 with 31x10.50R15's on them. I'm going to go with smaller 30x9.50R15 or 235/75R15 if I have to replace them though to get closer to the original final drive ratio. I love how the straight-axle Toyotas drive on smaller tires, myself. The steering and tracking feel much more precise on narrow, 28" tires and it brings the transmission gear spacing a little closer together. If you really want taller tires though, those SR5 wheels look great with 33x9.50's on them!
I'd even have a hard time re-painting it. It has such a nice, original patina. I'd just treat it to some wax.
If it were mine, I'd consider doing a round-headlight swap from a '79-'81 truck...just because you can! Here's someone on Yotatech who did the swap. I love the round headlight look.
http://www.yotatech.com/f114/anybody-actually-done-square-round-headlight-conversion-168542/ That's a matter of personal taste though.
Although they are pretty capable off-road in stock form, if you feel you want some more crawlability, the two things that have made the most difference for me are a differential locker and a lower low-range gearset in the transfer case. I went with a Lock-right locker from Powertrax for the rear axle due to the low cost and ability to self-install without having to reset the ring & pinion contact patch. They take a little getting used to but make a big difference in traction. I've had it in there about 10 years with no regrets. There are also selectable locker options that act as stock differentials when disengaged, such as the air-locker from ARB. A Toyota electrically-actuated locker from later 4runners and Tacomas can also be installed with a little fabrication. For low-range gearing, I went with a 4:1 gearset from Advanced Adapters. It was also a self-install and it adds considerable low-speed control and torque in low-range. Adding a second transfer case is also a popular option but I didn't want to do the extra fabrication or replace/modify the drive shafts.
For extra suspension articulation, the front sway-bar disconnect modification works well. I think they drive nicely with the sway bar removed completely but in order to maintain the most on-road control for emergency maneuvers, it's easy to build some quick-disconnects out of hardware store items so the bar can be disengaged for the trail. I used this design:
http://toyota.off-road.com/trucks-4x4/tech/swaybar-disconnects-toyota-cheap-tricks-18343.html
If you feel the leaf springs are beating up your kidneys, these trucks ride very nicely on a set of OME (Old Man Emu from ARB) leaf springs and shocks. They completely transform the ride without adding too much lift and are available in different spring rates. They increase the ability to absorb bumps as well as the amount of wheel travel and articulation. I went with the OME front leaf springs in the "light" variety but skimped on the back with just some add-a-leaves to save cost. Just the front springs made a big difference in comfort and capability.
Enjoy--those trucks are getting even more unique and desirable each day!
Here's a video you might enjoy--how to four-wheel early-80's Toyota 4wds from Toyota Australia (mostly Land Cruisers but some trucks as well).
Part 1:
http://www.youtube.com/watch?v=Xz0hN05GyLQ
Part 2:
http://www.youtube.com/watch?v=_D2rWt9M1q8
Eric
