As stated, I would go with 94-95 or 99+. The 96-98's didn't have the best motor build. . . but if you did get it at a REALLY GOOD PRICE (show em 6,800 cash or somewhere around there), you could always do the PI head swap (comes in a kit. . or you can pull the heads/intake setup off a 2004 GT) which will add about 50 or so HP without doing anything else to the motor =)
My .02 for ya.
Here's a link to the swap kit, I know a couple people that have done it on their 96-98 with great success.
http://www.parkwayperformance.com/2vheadswap.asp