Don't know of any kits to upgrade the bigger trucks rear gearing. haven't heard of any for the transmission either but they may exist. Auxilary transmissions such as Brown lipe are added for overdrive. Your truck should be ten bolt wheels front and rear with only five used on the front. Grigg has found there are some small bolt pattern 22.5 wheels that were used on some late 50's task force trucks that would get you 1 piece tubeless wheels. try the vin buster on this site to decode the number on the Id plate to determine what you have