you will get about 5 hp more than the stock PI mustangs(260) with all of the same PI parts, due to the bump in compression.. goes to about 9.5 :1 wich isnt bad by any means, if you do swap the heads, you wont be able to supercharge the car because the pistons wont like the compression with forced induction.. however, nitrous LOVES compression.. so if youre going that way thats the way to go.. you'll have to run higher than 87 octane gas, but who cares

the truck guys sound like they are sissys...
almost all of the 96-98 mustang owners that get seirous about modding swap to the PI heads/intake.
the only other thing you have to keep in mind with the PI headswap is your cam selection, the VT stage IIs that i mentioned above will cause your valves to hit the pistons with the PI heads on a NPI motor, however, the stage Is still fit...
or there is another route you can go, wich is what i personally think i'm going to do, the NPI heads arnt really the problem, its the intake that causes 90% of the power loss... you can get a PI intake, and adapter plates from livernoismotorsports (sp?), the plates are 299 and you can get a used PI intake for like 50 bucks.. it would gain you about 30 ish hp from what the NPI mustang has stock (225), your truck would be rated lower at 210 because of the intake it has (would be designed to make low rpm TQ, and not HP)
so you'll be 10 hp or so down on a car with the swapped heads as well, but then you still have the ability to use a supercharger if you want, or the more agressive cams (stage II's) etc.. plus the intake swap is a 1 hr job, the heads is a weekend job. you can get cams for the price of used heads, swap those in with the intake and
