I just picked up a 98 gt that is bone stock other then mufflers... They said the motor has about 50k miles on it and it was installed at the ford dealer.. Is there anyway to tell if it has the P.I. stuff on it already.. If not its cool as I have a complete 2000 4.6 motor at my dispense..
You could check to see, first of all, if you have the PI upper intake by looking at the first runner. If it goes to the drivers side it's PI if it goes to the passenger side, it an NPI intake. Not likely that the previous owner would put an NPI intake on PI heads, but you could have PI intake on top of NPI heads (like mine). PI heads are actually stamped that is not visible from looking at the engine, so don't know of a way without some engine component removal and looking for the stamping.