I did not use a store bought adapter.
I borrowed a hydrobooster and MC from a 2004 ford super duty, I think it is 1.625 bore.

I have also used the MC from a Chevy P30 chassis on another project, it is similarly large.

I have disc brakes on everything, so my exact suggestions may not work for you.

But, the idea is to go look in the junk yard or parts store till you see something that looks like what you need, even if you did not know what you needed before you went in, you may when you go out...

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-