I recently got a master cylinder and booster for a 1972 1 ton 4 wheel drive which they say is the same for 3/4 by the part number. My new axles are 4 wheel disc. Anyway I put everything on and noticed that the rod going into the back of the booster was tight agaisnt the firewall. I put pressure on it to get it to mount. When I pushed on the brake pedal it wouldn't move. I measured the bracket and it was like 3 and 1/2 inches from firewall to back of booster. So I went to a friends first gen stash and checked his trucks. I found all but one of his had brackets that were more like 5 and 1/2 inches from firewall to back of booster. I put the different bracket on and voila'. I also found the truck I took the bracket off had a support rod that went from the upper driver's side bolt on the back of the booster at an angle toward the driver's side firewall and mounted on a stud there. So I stole (I mean aquired that also). Just more screwed up stuff I ran across in my restomod saga!!