I am pondering the same thing, because i have a EFI 18R-GEU in my celica and it would cost about as much as an SR20 turbo motor complete just to do the custom mods and rebuild my motor to be turbo, before buying a new computer, bigger injectors, the turbo itself..
SO i am wondering if an SR20t (i hate to betray the toyota-only ppl) would fit well and be not much hassle.. They are common motors with lots of aftermarket parts available, Unlike the 18-RG or 3T-GTE.
I really want to build the 18RGEU turbo but i just dont want to fork out heaps of money on it only to have problems, because i know it wouldnt be easy sailing keeping it reliable.
while an sr20 is a newer motor of similar size and capacity, with 16 valve head and turbo internals from stock, with plenty of potential power for a street ra28.
IF only toyota had released another twincam 2 litre 4-cyl turbo in RWD layout!! i would also kill for a 3s-gte but the custom work involved there is a nightmare.