Seals are one item that I find quite easy to get at the auto parts stores either by the numbers on the old seals or by the dimensions of the bore, shaft, and thickness.
Sometimes they can look it up by application but it is still smart to confirm dimensions.

What seals are you looking for?

•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-