Back in the '70s I replaced a Pontiac overhead cam six in a Firebird with a mildly modified 350 Chev.
After I broke the Muncie I replaced it with a Saginaw, and as gas prices when up, I added the OD to the Saginaw.
Never had any trouble ever with the Saginaw. I kept the transmission when I sold the car, and only let go of that transmission a couple years ago, after one of my brothers ran in it several other cars.
I suspect driving style has a lot to do with how long they last.
