I don't know of anyone selling a rebuild kit for the '60-'63 or the 4-5-6 chevy truck window regulators. Here is a link to LMC Truck, but they don't sell them either, only the replacment window regulator.
http://www.lmctruck.com/icatalog/cbe/full.aspx?Page=13
I have several good, used window regulators, if you want to go that route. Let me know if I can help and good luck with the search.