According to this PDF, if I'm reading it right, it is an interference engine: http://www.gates.com/~/media/files/g...uide.pdf?la=en

1999 3.5 V6 takes a t287 cam belt and is marked with a star, which should indicate interference.

Another option, since it's at a fairly high mileage engine, is to just drive the thing til it goes and replace the whole engine with one that has way less miles. Aside from the massive PITA that is, is there a mechanical consideration I'm not aware of which would say that's a bad idea?