I think it is a gasket issue, the only ones I have found that are close to factory height are the ones that come in a full kit from NAPA, the Fel-pro ones are alot thicker.
The Fel-pro ones for what I have seen are about 3/16" thicker.
These thicker gaskets seem to be common with GM and Ford OEM applications starting in the mid-1970's. Wouldn't be surprised if the gasket manufacturers simply tooled up the Mopar-application gaskets with the same material as a cheap alternative.
There might be a vendor for the proper ones on eBay. Saw a few on Google Images that looked similar to the material used on my Valiant's gasket.
If all else fails, try calling up Just Carburetors, Inc. - they're a few miles away from me in North Miami, but the owner (and only man operating the show), Omar, will not only have what you need, he'll probably know exactly what's going on with your setup before you finish explaining it to him over the phone. One of the best (and most knowledgeable) of the carburetor specialists in the country.