What Rex posted is exactly what I'm looking at getting. Just under $20 at several retailers. I've been looking at Sherman gears because the overall width of the VS model is the same as the half-tracks I want to convert. If the INTERNAL width is the same, it doesnt matter.
On this build :
http://www.desertarmor.com/DAK_PROJE..._250.html#grid he managed to get panzer 3/4 1/16 tracks to fit the stock sprocket and wheels, so as long as the VS sprockets can be removed, everything is gravy.
Anyone have a 21st Century Sd. Kfz. 251/22 Half-Track with PaK40 75mm for sale? They're out of production :P