do you have any pictures of the carb?
It does sound like a 4200, the 9 maybe an S, sometimes the numbers and letters are not clear.
Your fuel inlet should be in the front right air horn?
and both sets of venturi's will look like the same, the rear set will be attached to the side of the float bowl not the rear as most others are.[FONT=Arial][SIZE=3][FONT=Arial][SIZE=3]