It is possible that exhaust is blowing into the intake through a crack, which would definitely throw things off. There is no plate in there, just the castings that separate each other, but they can corrode too. 

On the carb, if it has been sitting, it might be a good idea to take it apart and clean everything up. Could be a sticky float or needle, could be the float has been crushed by water freezing in the carb.

The 1750 gas had the 283 gas engine in it.