4 speed identification

Just FYI
40 years ago, makes it 1970. So it would be a low-mileage unit.It sounds like it could be a gem.
Since I was a transmission rebuilder at one time, I, of course would go through it.
On the other-hand you could probably slam it in and go. To you, that could make it worth a little more. Not having to purchase;bearings, gaskets, seals,and blocker-rings, plus labor, can add significantly to an initial purchase. I have had to charge as much as $850Can to recondition those.(no hard parts)
Best of luck to you.