Hello Kelly and Welcome! I think the 1 ton master is the same as the 3/4 ton, but not sure. That size is readily available at Classic Parts, Jim Carter, American Classic and maybe even your friendly local auto parts store. You can research Keith Hardy's info on
http://chevy.tocmp.com He has posted on there re-prints of original shop manuals, etc. Maybe somebody else will help. Good luck
Edit - I just flipped over there and the master cylinder is the same diameter for 3/4-ton and up. Look
here .
