what would be the better n/a engine b16a, b16b, b18c, b18c from a itr

 

whatever you want

all of those listed engines can be built to really great and strong NA setups, just depends how you build them.

Out of all I'd take the b16b or the b18c5, both would make awesome engines to run

 

what would be the best bang for the buck

 

b20 block b18c head