[toomanybirds]

Dick is correct on the trans codes for the 73 M20 Muncie 4-speed. The UA was the early (pre-emission change) code. WD was the late (post emission change) code.

The only difference is the location of the TCS switch, it is on the 1-2 shift shaft on the UA and the 3-4 shift shaft on the WD. The early emission system added vacuum advance on the 1-2 shift, the late system added advance on the 3-4 shift.

As has been discussed before, all 73 SD cars came with the wide ratio M-20 Muncie trans, and all were built after the emission change. So the correct trans code for a 73 SD car is WD.

I know of only one exception to this, I have seen a 73 SD TA with an M-21 trans. It has the vin stamping and appears to be authentic. I believe it to be an assembly line error.

I think only a few cars came with the tag on the left side of the trans. I have not seen one in place on some very original 73 cars. Brewster, your green 73 doesn't have a tag does it?