Krylon Fusion
BigDan - On my old '96 Dodge, I wanted to do the semi "sport" conversion. I first had the best painter in town try it - he did it twice and the paint peeled and flaked within a couple of weeks and got worse in rain.
Luckily, I hit a hit a deer :-laf and got the thing replaced. I then had the best body man in town give it a try and the paint chipped off after he did it too.
Do a search on here - I posted about this very thing over a year ago. The paint you want is Krylon Fusion and you can get it at Wal-Mart for less than $4 a can. It is the only thing that has won the approval of TDR members and all of them have said that it has stayed on their truck. I have asked around town here about it and everyone says it's good stuff. Give it a shot.
Oddly enough, I'm having my grey plastic painted white with the Fusion paint next week. We'll see what happens...
Good luck.