I have a M20 Muncie I believe from around 69. The numbers are filed off (I wonder how that happended?). It has the levers that use nuts not studs. It has an attachment? on the base of the 3/4 gear lever housing that looks sort of like a speedometer cable attachment. It is a large nut and looks like the male end of a speedo cable. (It has a normal speedo hookup on the right side towards the rear). Anybody have an idea what that is?

if the transmission is a 70-up model, its the switch for the TSC, it operates a solenoid that supplies vaccum to the vaccum advance only when the transmission is in 4th gear, in your case, or on an automatic, it works in drive.

Guess what, someone before you has been into that tranny. Or, put it together from misc parts. The side cover is a 70-later with a Transnission Control Switch (TCS). The correct switch which goes in that hole has a hex hesd (a 7/8in wrench) and a single blade terminal.
Which numbers are filed off, the casting or the stamped numbers? If it is the casting numbers, you may have one of the rare cases that for whatever reason GM removed them. If it is the stamped numbers, maybe it was at one time stolen and someone tried to remove the identification.
If this is a 68 case, then 68 was the last year for studs, but 70 was the first year for a side cover with a TCS hole.
ANY 63-74 side cover will physically fit and all the shift lever parts will interchange and work.

------------------
Tom Parsons

Your right, the guy I bought the tranny from rebuilds them from parts, so no telling what combination of cars it originally came from. The numbers are actually hacked up with a chisel. I suspect stolen at one time. I have it behind a 250 6 cylinder in a 68 Camaro RS. I guess I don't need the vacuum advance hook up. Thanks for info guys.