I had a leaky master cylinder when I bought the car over a year ago. Apparently it leaked into the booster. I replaced the MC with a Dorman unit that seems to be a great fit, but I still have hard pedal, and my vents don't work so good- I suspect I'm losing vacuum through the booster. Rebuild kit for the booster is almost $300 from Fusick, if you think you can get that unit open after 60 years, or you could get the unit for about $700. There's a guy who sells a set up with the booster and MC on ebay for about $400- but I already bought the new Master Cylinder (MC) and I hate to waste the cost of the MC, it was a hundred bucks. Summit Racing sells a booster, universal fit (which means it'll work if you can make it fit, of course). It's part number SUM-760124-BLK, and it's a really good fit except where it's not. It needs a 1" bracket between the back of the unit and the firewall, and a longer push rod. And they're metric- that was a surprise!


A bracket to make up that distance is important, but it would probably do the job well

total length is a good match- again, I need a mounting bracket

1" threaded coupler, and I'll have to cut the mounting bolt so I can screw in a threaded rod. I'd probably want to tack weld it.

Or I can fab up a bracket with bent metal, but I'd still have to weld a carriage bolt or something so I can fasten it to the firewall behind the brake pedal.
The couplers would be easier I think, but I guess fabricating a really good looking bracket would be more professional.

Humpf... professional. I'm going to use a piece of steel I have laying around, bend it over a hunk of landscape timber using a clamp and a hammer, drill a hole with a hand drill and a couple dull drill bits, grind down the jagged edges so I don't cut myself on it, spray a coat of black rattle can... I'll weld a carriage bolt to the back side so it goes through the floor where I can bolt it to the firewall and adjust the pedal throw, and hope the pedal ratio is something that works. $400 on Ebay is starting to sound like it would have been a bargain...

 

Personally I've had a lot of bad experiences with aftermarket master cylinders, I opted to send the originals off the Karp's for a rebuild. I haven't driven it enough to put a quality verdict yet but I'm confident it will be better than the Chinesium out there currently.