Are you sure you have a Saginaw? If first gear is not synchronized, then you probably have the Muncie SM318, although it is often referred to as a Saginaw. It's the most common transmission they used in the 6cyl cars and 1/2 ton trucks back then. It was available in the trucks until around 1967. As OldSub said it may last for years if driven easy, but they don't like abuse. I had a mild 327 in my first '65 pickup as a kid, and I busted several of them. But of course I was asking for it. Best of luck.
TruckNut
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