Solved! Well, at least on paper.

I have decided to use a new MICO mechanical caliper. A 13 or 14" by 1/2" thick steel disk welded to my output yoke. And a Bendix spring brake chamber specifficaly made for parking brakes, their number SB-1.

I have yet to find the chamber, or make the disk, but the caliper will be here in a day or 3.

Thank you all again for your help.
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-