Hello, According to http://www.cubcadet-parts-direct.com/wp ... s/logo.gif
the deck belt is a 1/2 x 72" They don't give the size for the drive belt but they list an IH part number, 478881-R3. I went to the NAPA cross reference and that came up with this - 3VX850. Hopefully that crossed correctly, it's a .375" (10mm) x 85" belt. The Cubcadet look up shows the 42" and the 38" deck use the same drive belt. For what it's worth I use the A series Power Master belts (1/2" belts) that Gates makes for both the drive belt and the deck belt on my 104 Cadet which is also supposed to use a .375" drive belt. They work very well and last a long time. NAPA, Carquest, and others sell the Power Master belts. Places like Tractor Supply don't seem to handle them, they definitely do not stock them.
Hope that helps you out.