OK...I'll go along with that... My measurements were from the front of the gearbox (where the bellhousing attaches) to the back of the driveshaft flange.

The difference is only a quarter inch, and some driveshafts might be able to pick up that slack in the splines. But not necessarily all of them. I doubt the spacers between the OD and tranny are interchangeable Some are aluminium, some iron...though maybe they do interchange. but...heck, I don't even know if the output shafts of the transmissions would work from one to the other....????

In any case, I'd bet that y'alls interchange between J and D tipe overdrives only worked because you had enough slack in the driveshafts to take up the difference in length...

For that matter, I only measured those out of curiosity based on Sutherland's experience with his originally automatic converted to OD car... and someone might well have messed up the driveshaft measurement in the first place with his car....?

I've torn apart several M41s, but I've only put one back together, so my knowledge is a bit limited in this regard..

-Matt