any engine... with the right amount of money...
These are the simple swaps... GA would need a diff gearbox however the SR series will swap in with the most ease... most need the loom to be spliced and minor flywheel adjustments however they have all been done with relative ease...
Don't forget you can always bolt on a turbo to any of the below engines... But more work...
And if you're thinking about sourcing a SR20VET... you're dreaming.. or if you are serious... you have a lot of money to throw at it...
GA14DE
GA15DS
GA15DE
GA16DE
SR18DE
SR20DE
SR16VE
SR20VE
SR16VE N1
SR20DET - U12, U13, RNN14, PNW10, PNW11
SR20VET