I would love to have that extra gear

 

My 98 Cobra is getting a whopping 14.8 MPG. Darn those pesky 4.30 gears and........

 

Acctually you should make really good power. The 96-98 cars had flat pistons so when they would swap to the 99+ PI heads, they made more power than teh 99-04 cars did with teh same heads. The flat pistons created a higher compression ratio. Now I dont know how they are addressing this on the Trick Flow pieces, but regardless you should be better off.

 

I read more about the trickflow heads and they are offereing them in a larger chamber size for the 96-98 guys so compression won't go up if you buy that version.

 

I think I would probably swap out the intake and cams too, but with Mustang resale values in the toilet it seems like buying a 99-09 would be the cheapest route.