Having "too small, too large" does not necessarily denote Q-Jet, depending on the poster's definition of small and large.
Many of the "square bore" intake manifolds have "2 small, 2 large" bores, where there is about 1/4 inch diameter difference from small to large.
With the Q-Jet manifold, there will be between 3/4 inch and 1 inch diameter difference from small to large.
Once you have identified the engine, this page from our website will tell you the correct carburetor:
http://www.thecarburetorshop.com/Kchevrolet3.htm Jon.
