Wanted to do an engine swap. I was looking at swapping with a 2jz, but wanted to see if I would see any gains.

 

This is a pretty open-ended question......

There are two "2JZ" engines, the n/a, and the turbo.
2JZ-GE: (212–227 bhp)
2JZ-GTE: (276-321bhp)

There are several well known S30/S130 2JZ-GTE engine swapped Z Cars. It can be done, but the limit is the $$$ in your bank account, and the skills / knowledge you possess.