Helping my friend with his truck and my realm of expertise is more in domestics. Can anybody tell me if it is possible to convert the automatic locking hubs on the D21's to manual hubs? If so, who makes them and what all is entailed i.e. do you simply disconnect the electric button on the dash, are there any modifications necessary to install the manual hubs etc. And if not, are used automatic hubs the only route? He already called the dealer and they said the hubs are no longer available. Thanks in advance for your input.