There are a couple vendors selling the large opening reproduction base plates, however all of the steel versions are similar in price (EXPENSIVE!) you can shop ebay to get a feel for what they run.
Your other option is Hemi clone carburetors (also expensive). I build them to order and sell quite a few to those who want a stock appearing setup that costs many times less than an original set of Hemi carbs cost. These not only look very much like original Hemi carburetors, they also fit the factory inline intake manifolds (that's an original Street Hemi intake they are resting on in my pic) and accept all of the factory style Hemi inline dual 4 small parts, linkage, fuel lines, air cleaners, etc. and modern Edelbrock jets and rods can be used to tune them. Available in 600 cfm, 750 cfm, and 800 cfm sets.