the rear disc brake kits or brackets are often sold or advertised that you can use a "Cadillac caliper with parking brake".
In reality those calipers are expensive, or hard to find cores for them, and I've seen it mentioned several places that they're not the most effective parking brakes.

Which means if you don't have parking brake on the back of the transmission then converting to rear disc with those brackets might not be the best option.

•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-