76 Miller,
Both Weiand and Offenhauser offer cast 2x4 tunnel rams. The Offy comes with SCJ-sized ports as cast, and the Weiand has passenger car-sized ports as cast but can pretty much be ported to SCJ-size.
Since you have the ProCrap cylinder heads, you should probably purchase the Weiand since it has ports that are the same size as the ProCrap's intake ports. It does require some detail work in the plenum area but the results exceed the effort put into the cleanup of the plenum..
LO