I don't know about a 2nd gen conversion, but i do the 3rd gen. Personally, i wouldn't convert to 2nd gen, but do 3rd gen!!! The body styling looks so much better, almost like a muscle car the way the hood lines are smooth, yet robust.
Not sure about conversion KITS, but i know 3sxperformance has the materials to do a 99 body conversion here:
http://www.3sxperformance.com/body.asp . Personally, i don't like the look of the 99 rear garnish tail light. If i were you, i'd get a GTO rear garnish tail light.