Help on 96 mustang GT

Use the pi heads and cam on the good motor. The 96-98 had crappy heads(non pi), in the 99-04's they came with pi heads(power improved) which bumped the commpression and also brought the hp from 215hp(96-97) 225hp(98) Up to 260(99-04). You will gain a decent amount of hp and some torque from it. I believe also switching to the pi heads you will have to run premimum fuel as well.

you don't have to use pi heads

If you plan on a supercharger or turbo down the road stay away from pi head, and just port the stock npi heads, they will flow better than stock pi heads and will not raise your compression. if your not going to supercharge or turbo, you can either put the pi heads on stock or ported....or ported npi (stock heads). The biggest restriction of the npi motor is the intake manifold, if all else fails atleast change that. npi heads just aren't as bad as people make them out to be they are just not as good as pi's.