Kent,
Your best bet is to place a want-ad in the Swap Meet. For a Chevrolet, any 58-62 air cleaner would work. All Chevrolet trucks came with one-barrel Rochester carbs that had the some throat size for an air cleaner. That style air cleaner works with a carb that has a bolt coming up from the center of the throat (I do not know what year that started - maybe 1956)?
Dave,
A GMC air cleaner might be different - isn't your carb a Zenith carb?
Tim
