The Stovebolt Site Forums The Shop Area Driveline Drums to Disc - What Master Cylinder to buy

I am in the process of converting my rusted out and missing drum brakes in the front of my 53 GMC 150 and replacing them with Disc Brakes (from 2007 Savana) using this forum thread. https://67-72chevytrucks.com/vboard/showthread.php?t=647049
What new master cylinder should i purchase? I know I want a dual master but I dont know what bore or size. Any help is appreciated.

If you want to keep it GMC the 2004 Savana was the last disc-drum dual MC and will work. Most use the Corvette style cast iron dual MC that has brake line connections on both sides and can be ordered for disc-drum set up---$50 at Speedway. You will need power brake booster with the discs and easiest to work with and bleed is one firewall mounted.

I would disagree with Evan that a power booster is "needed". I've had it with (current '52 152 came to me with power disk brakes) and without (my '57 102 that I installed a disk brake kit myself). Both were certainly useable. I used a late 60s/early 70s Mustang master cylinder which has built-in residual valves. Mounting in the stock, under floor location is easier without the booster.

My 51 has the drum /disk with a dual mc and it works great. Go for it

https://www.performanceonline.com/1947-55-CHEVY-GMC-TRUCK-POWER-BRAKE-BOOSTER-KIT/


The real benefit of disc brakes comes with the power booster. All the new masters will be dual.
I would not do the conversion with out a booster. It does not add any complexity or problems to the upgrade. The under floor master available in disc/drum and disc/disc.