definately consult an engineer about this if you want a turbo one, it may not be allowed.
Sr20 is done to death, easy conversion as far as conversions go, from what ive read people have more trouble with 4ag coversions.
The 3s beams is popping up a bit, i like!
1ggte fits, depends what you want out of the car though.
People are getting 100rwkw out of simple efi forced 5k conversions, with the lack of extra weight, this is really cool!
3tg, 2tg, 18rg, all classic retro cool motors,
vg20 would fit, and be legal, do that.....
What I'm saying is do your research, and decide, it up to you!!