I bought this earlier today. Reportedly all C6s with the FE bolt pattern and which were made from 1972–197? (the end of the 6th gen F-series run) are essentially interchangeable.
So I've got a used unit out of a 1975 truck that had a 360 or 390 in front of it. I'll be tossing it into the truck once the heat abates.
I forgot just how easy it is to lose fluid out the tail housing so I lost a ton of ATF out the back of this thing on the 50+ mile drive home. It got all over the bed, the rear window (sprayed there by the wind) and dripped all over the muffler as I was driving making loads of smoke at every stop light. Awesome.
P.S. if it doesn't work out in the truck, I'll find another FE engine and drop it and the C6 into the Craftsman mulching+bagging unit there in the background.

Are you planning any sort of rebuild on the transmission you just purchased?
Nah. The seller assures me it ran fine when he pulled it out. I seriously doubt it could be any worse than the one I've already got in the truck.
If I find out it runs like crap, I'll just rebuild the one I pull out of the truck, and then swap it back in.
--D
Also, the seller was an independent auto shop, so the odds of me getting scammed are fairly low.
Someone was in a BIG rush to remove that from whatever vehicle it came from. Note the speedo cable was cut off the back rather than removing the ONE bolt that holds the gear in place. Does it have serial numbers?
Oh yeah, it ran fine . . till we stole it.
Funny you bring that up--the guy mentioned that he typically leaves the pigtails on all of the lines when he pulls parts so the hardware (said "ONE bolt") doesn't go missing.
Also, time is money.
--D
The aforementioned "ONE bolt" is a lot cheaper than a new speedometer cable.
Is there really a market for used speedo cables? I'm not sure I see the point in pulling one off an old truck.
Clearly there's a market for used transmissions.
My speedometer cable turns itself inside out all the time. When its not bouncing or until I get to about 40 mph.
My speedometer cable turns itself inside out all the time.
What the deuce??
--D
Wait is that some sort of ancient Officer Barbrady reference?
Nothing to see here people.