[JM 35 Sedan]

Gregg, check to see if there's a serial number stamped on the flat area above the sheet metal clutch inspection plate, held in place by two fasteners, on the bell housing of the transmission case. This number will give you the month and year that transmission was used in production, based on the serial number listing on Mac VP's website. There is also a number cast into the back of the transmission gear case that will tell you which series, and year/manufacture case you have.... 18-xxxx, 48-xxxx, or 78-xxxx.
Also, if you could post some pics of the gear assembly and shifter top assembly of your transmission we might be able to provide further information or advice.