Yes...it will fit...there are 2 major types of swaps.
The first popular swap PI heads and the PI intake on an nPI 96 – 98 Mustang resulting in an approximate gain of 45 RWHP, but with an increase in the compression ratio to approximately 10.5-1 making these PI head swapped engines supercharger unfriendly.
Another common swap that involves less labor at significantly less cost is the PI cam and intake swap. The swap provides a gain of approximately 30 - 35 RWHP while maintaining the stock compression ratio. Because used PI cams and used PI intakes can usually be purchased for approximately $100 each, this mod is proving to be one of the best dollar for horsepower mods available for the nPI equipped Mustang.
I suggest getting the heads if you have the money. It is great for poweradders ect to have these new heads.