I love my 71hta. Makes 450/400 on E85 at 30psi. I made 403whp at 25psi on our crappy ACN91.

 

Pretty much the only way he's going to make a true 500whp on 91 is a large turbo. Like an HTA3586 (or the new Xona equivalent), and it will need cams, and maybe even an intake manifold. An FP black will proba do in the mid 450whp range. Both will be laggy.