I would not assume that a gearbox this old is "as built." EASY to tell if OD or 4 speed
One way is if the linkage "fits" right and the front shift lever is pointing down instead of up. Otherwise............
Just put the thing in 3rd gear. You do this by moving the front shift lever CLOCKWISE, which moves the internal shift fork to the rear.
Rotate the TAIL shaft 1 turn and count revoloutions on the input shaft
Actually all you need to find out is if it turns MORE or LESS than 1 turn
If less, it's a 4 speed
If more, it's an OD
If you are unaware, all the Ma did to build these (basic) was to revamp 3rd gear into an OD ratio, then turn the front shift lever upside down. So when a 4 speed is in "high" (4th) the upright shift lever on the box moves the fork FORWARD (CCW)
When an OD is in high (old 3rd, new OD) the upside down shift lever moves the shift shaft to the REAR (CW)
In other words, in either box, the "straight through" gear, high in a 4 speed and 3rd in an OD is the same gear. It's just that the shift lever makes you "think" "straight through" is 3rd in an OD box.
