One came on my 71 small block Camaro. Also had 26 spline input, large output M20. Wasn't that the standard for all Muncies in 1971?
Correct, in 71 ALLLLLLLLLLLLLLLLLL Muncies got the 26spline input shaft and the larger 32spline tail shaft.
MANY, MANY, MANY people in the past have MISUNDERSTOOD that the fine spline input/big tail shaft Muncies were only M22. NOT SO! And it has been an uphill battle to convince them that just because a Muncie has the fine spline input and big tail shaft, it is not necessarily an M22. But I think the message is finally getting across to most of these people.
I can only guess that the reason for this incorrect understanding is that in 1970, the Chevelle with an LS6 engine and M22 did get the fine spline/big tail shaft Muncie. But for 71, they were all fine spline/big tail shaft.
When the Borg Warner Super T-10 replaced the Muncie (1975), it also had the fine spline input/big tail shaft.