I checked the bore of both new and old carbs.  Used a tape measure as I didn't want to take the time to find the dial calipers.  IF the Zenith bore is smaller, it is only by 1/64th of an inch or less.  FWIW, the 88 intake has a sort of venturi taper in the mouth of the intake.  When mounted to the old 88 manifold, the Zenith studs snugged up very close to the inside edge of the carb mounting holes.  There was no fore and aft movement along the line of the holes, but a little side to side movement could be made to happen, but then on only one end at a time.  The only reason this carb will fit is the smaller diameter mounting studs on the Zenith.  I agree that the proper course is to get the right carb (whatever it really is that I have), was just hoping to save time, additional shipping (another carb and returning the Zenith) and the 20% restocking fee (OUCH!).

Ed