Thanks to all of you very knowledgeable Mopar people on this list--it really does appear that my '57 Plymouth Suburban wagon with the Fury engine and dual 4's is a "factory ordered" original. The car has only had two owners, and just after I wrote this question to the listserver, I got in touch with a guy that knew the second owner. He says that the car was indeed special ordered with this engine, and that it is probably quite rare. Anyway, it is a gem and I really appreciate the input from you folks! Jim Helm