David,
I went through R&J and had a GREAT experience with them. The items are really nice. I got the "combo kit," RJ35207, which consists of the M3 Wheel Set (drive and idler wheels in resin), the M3 Halftrack set (tracks in resin), and the M3 Halftrack wheels (front wheels in resin). This is all for an M16 I'm doing. Great company, great service, and great products! I now seem to have a spare set of the resin front wheels (mistakenly got a set of TWS off eBay...silly me). Might be able to help you out if you don't go the combo route.
HTH,
Mike (++) (++)
p.s. Paul is a WEALTH of knowledge!!

and likes Fat Tire

:-)
{Edit - Drader, nice link........I'd like to do the same sometime and this link was pretty darn good.}