Most likely a 1962 to 1969 model SM420 transmission, and obviously a compatible PTO.

Hang on to it, or give or sell it to a fellow Stovebolter, someone will be happy to have/use it.

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-