a complete GSR setup or a gsr block with a b16a head?

 

well, with the 1.8L bottom end and 1.6L head, you're gonna have air intake issues. in order to have the most efficient running motor, they must be port matched together to ensure equivalent displacement of air and fuel. this can only be done by top engine builders on a special bench called a engine/head volumator.

 

A gsr will be faster. Switching to a pr3 (b16a head) will lower the compression resulting in less power.