There are at least two versions of the "2GC". Your 283 is going to need the small-bore model. The bigger-bore carbs were used on engines like the 389 Pontiac, and a couple of other, bigger engines. That one will run far too lean on a 283 due to bigger venturis than needed. When that big-bore carb was used on the mid-1970's 305's, it was necessary to set the float level extremely high to compensate for low venturi velocity. 30 cubic inches less engine would make the big one almost impossible to tune or drive. The 305 manifold also doesn't work on a 283 because the 2-BBL bolt pattern and manifold bore size is wrong for the small-bore 265/283 carb.
Jerry
