Great looking rig! I have an 87 with a g54bt in it on 33 bfg km2 with some toyota shackle lift, roof rack, and soon to be sr rear locker and front arb.
My next swap will be a diesel though. You can pull about 28mpg out of a 4d56, and the reliability is excellent.
Mine isn't as pretty as yours, but I take mine ito anything and everything lol.I wouldnt bother with a 4g63t swap, you will want the extra low end powerband of a g54bt over a 4g63t imo, Especially when going with larger tires. I suppose if you changed the transfer case gearing it would be find, or double transfer cased it.
I'm assuming you would run some toyota trans if you went 4g63t.
Lately I have been thinking about runnign a divorced transfercase like a atlas, in with a starion transmission to beef up my current drivetrain. The stock trans are pretty damn weak.
My last excursion new years day
31 3000gt vr4
88 starion x2, 83 starion
88 cordia turbo
87 Montero swb turbo, 1987 Minicab van Supercharged
86 mighty max 4x4
84, 85, and 86 lancer ex1800 turbo
73 galant coupe
65 Debonair Deluxe