Hi Rob,
Regarding your questions I can offer the following:
Chrysler used the "DELTAWING" (proper name from Chrysler) for thier 1955 C300 and 1956 300B examples. These look the same on the outside, but the pods are different interior between years. In other words, I've found you can't interchange an inter with an outer from different years. DELTAWINGS are the only ones that have four (4) indented ribs running fore and aft. All others I've seen are smooth on top.
DeSoto had a version only for their 1956 Adventure and it is different as all others regarding placement and height of the necks to attach to the carbs. Also, there are Caddy, Chevy, Pontiac and Packard versions out there. They were all made by A C Delco and some mounted with the V pointing towards the firewall.
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To find the correct DELTAWING for your early Letter Car can be expensive, so make sure you get what you are looking for. I would suspect the DeSoto versions are also rare and costly. You mentioned Dodge but I've never seen such.
In conclusion I'd verify the manifold will fit your motor and then mount the carbs and carefully check spacing against air cleaners you may find.
Best of luck in your search,
John Lazenby
Model Year Consultant Chrysler 300 Club International, Inc.
C300 & 300B