There are several companies that sell a bracket and dual master for your truck.
If you are confident in your abilities, you could find a truck or large car similar to yours that came factory with a dual master and four drums, then go to your Friendly Local Auto Parts Store (FLAPS) and buy one.
If you want to spend $100+ on a bracket you can buy one aftermarket. Or you could search the postings here for pictures of the bracket, and maybe look at the catelogs/webpages to get an idea of the bracket's shape and configuration and then built it yourself.
If you can't build it for lack of a welder or grinder, you can make it out of cardboard and take it to a metal shop where they can build it for you.
Try the search button at the top right corner of the forum home page and read a few of the threads posted here.
I bought the master, bracket, combo valve and proportioning vavles with a booster for my '51 (disc/drum) from CPP. I wish when I had bought it that I had gotten a dual diaphram for $30 extra just because with the cam in my engine at speed I've got less vacuum. Next time I do it I'll build my own bracket and buy a master and 7" dual diaphram booster from a mustang.
'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi
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