actually...your best choice would probably be the b16's....if you still have the p72 head

the ctr's yeild a very high compression ratio with th gsr head...due to the smaller combustion chamber (square shape)
depending on you cam choice you might have valve relief issues

with the b16's you wouldnt have to modify the rods either
(i think...because on b18a' or b18b's you need to shave the top wrist pin to clear any of th R type pistons)

anysways go forth and get some porn...it helps with any mod