Yes, you certainly can! In fact, this is a very popular upgrade for 96-98 GT owners. So popular in fact, there are many guides scattered all over the World Wide Web that detail the process in-depth.
To complete the swap (a quick Google search for ‘pi swap’ will yield a TON of results), you’ll need to pick up the PI heads, intake, and a few odds-and-ends (hoses, brackets, gaskets – that sort of thing) in order to complete the swap. You can buy both the heads and intake brand new as they are still produced (in fact, even aftermarket companies make their own version of this head) or purchased used off a fellow Mustang enthusiast, from the scrapyard. These heads are available in plentiful numbers. If you decide to perform this upgrade, sourcing the parts is not going to be a problem. It is a pretty in-depth procedure based on the fact that the top end has to come off, but with attention to detail and much patience, the average Joe can do it in their driveway. The trickiest part may be getting the timing set up correctly after the install. Other than that, it’s nuts and bolts.