I can't give you a solid answer to your question. My gut tells me it is possible. My brain asks why you would want to make this swap? You would only gain the super low granny gear. You would lose the syncros the 3 speed offered. This swap will not make your truck go faster. It doesn't seem like a great tradeoff, unless your 3 speed was dead and you had the 4 speed in front of you. The brake cylinder bracket will have to be modified to work.

Orinda isn't too far from SF, and there are plenty of members on this board that live around the bay area.

Welcome to the "Bolt"

John