I have a 77 Trans Am motor, factory low compression. Am I better off with a 72 cc head to boost compression or the larger 96cc and up? I would like to be about 9.5 to 1. Thanks, Max  

The 72CC heads with a flat top piston will give you a 10:1CR which is too much for pump gas so I recomend a head with a 89CC chamber which will put you around 9-9.5:1CR.  

Another approach is to use a 72cc head with dished pistons (KB makes them).  This produces 9.6:1 CR.  Of course this would require considerably more work and $$ than just a head swap.