All depends on what you're shooting for. Street car,autocross,drag racing,track,etc.etc. So many options for this car out there. 4AG is the most popular. I've seen some built 3K motors. Rotary for the drag Starlets. Maybe you can even do the S2K swap.
Keep us up to date !

 

I've trying to source a 3T motor and do a mild build. A F20 would be really nice but way out of my price range.

Will do about the updates.