From what I have found out on line and from my shop manual (1947 AD (Thriftmaster) or 1947 second series) is that the '47 came with a three speed on the floor with synchros or a four speed without synchros. The SM 420 wasn't used until 1948.My transmission is a four speed with no synchros. There is a reverse lockout lever rod that runs along the side of the shifter which is activated by lifting up on a 'tab' to the right and just below the knob. On the SM 420 you push down on the shifter and put into reverse position. My transmission has a PTO plate.

It's a small world, but I wouldn't want to paint it.