Grigg,
The AD cabs traded the side cowl vent for the vent windows in the doors in '51. All AD cabs have the top cowl vent.
I have both an early '49 (January) and a late '49 (August) and the cab mounts are the same -- two bolts with pads & spacers in front, two shackles (one on either side) in back.
The only difference between my two cabs is how the center of the headliner attaches (early one has the screwed on bow, the later one "floats" (has a ribbed retainer that the edges press into).
Woody -- no brain farts -- only opportunities to learn
The Advance Design series started in the second half of '47.
Regards,
John.
