It will all depend on the axles you have, and if they will accept the brake components you want.

Most big truck axles have pretty standardized wheel ends, so you have a few different brake choices for any given axle. Don't expect this to be true for old stuff.

I think the answer to your question is you just buy the individual components you need, and there are no application specific kits already assembled for you.

When you say air brake conversion, what are you converting from? If it is hydraulic to air there are lots of parts needed, including an air compressor. You may be better off buying a junk truck like yours but with air brakes and swapping all the stuff, be sure it has the same model axles first.

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-