From what I'm seeing, all of these are for modded engines.
What's the bare minimum setup needed to get it running and driving, but not necessarily racing?
This would mean either the stock 2JZ twins or a CT26 from a 7M if the twins won't physically fit, R154 with stock clutch, stock ECU, hacked together harness based on the stock 2JZ harness, homemade 3.5"-4" straight and downpipe, radiator and intercooler, mounts, turbo line stuff, necessary fuel tank and oil pan, fuel lines, etc.
I have a buddy with a Mk3 with a 60:1 CT26 and a K&N filter that's pushing about 280bhp, so I know the stock R154 clutch shouldn't slip at stock 2JZ power.
Basically, get it from a daily driver with an L2x to a daily driver with a 2JZ.
After that, the order would be basic performance mods to get the engine running happily to get better gas mileage, chassis reinforcement and complete overhaul of any rust spots (Weight be damned in this part. Still lighter than a stock Supra. Engine will pull), basic bodywork on any rust spots (Sanding, Bondo'ing, rattlecan seal), brakes (Will the stock Mk3 brakes work?), fully adjustable suspension (Similar to the full Tein kits with the computer that actively adapts the settings), a few more performance mods (Bigger turbo, injectors, MAF, top end rebuild kit, etc), aero body kit (Front lip and moulded spoiler. Maybe a rear and bottom diffuser, if I can afford it), a real paint job, interior (My long-time girlfriend is a taxidermist, so this leaves some rather interesting possibilities, plus we both have an interest in steampunk/dieselpunk designs. Wood lacquered black/dark brown with brass seams. The brass would more or less cover up the fact that we're neither one skilled enough with wood to work the dash as a single piece. Dark leather seats, gauge needles made of clock hands. Not the shit you see on Deviantart with gears glued to everything with absolutely no reason to it), and then wrap the whole thing up with rims.
After that, I'll finish paying the bills and start work on the next project. A "classic" R35 GTR, maybe?
I'm not a mechanics expect by any means, but I'm learning, and my best friend was the owner of Stroke It Imports before their supplier decided to sell to the masses and they lost their market edge and went under.
That said, labour will be reasonably cheap, probably paid for by buying him some carbon fiber parts for his MA70. Maybe doors.
Other than that, I go to a technical school for computer stuff that has a welding program, and it is not too uncommon for projects to be brought to second year students and all you pay is materials. The quality is about what the average hobbyist could do at home. The novice skill is offset by quality welding stations and expert supervision.
If I don't go with a 2JZ, I'd go with an RB25DET. If not that, I'd go 7M.
If it wasn't for the torque the engine makes, the 7M would be higher on the list, if not first. 280 ft·lb of torque (With the wastegate pressure put to 10-12psi. Probably closer to 300 with a straight pipe) would be miserable in a 2300lb vehicle until I snagged some super wide rims. Probably close to what the Viper ACR uses.