Ok, here you go, mystery not solved...


"Looking at the 3 pictures you sent, I don't recall any cast aluminum parts we did in production. These look like just like the sheet metal parts made in production by Canadian Fram in Chatham Ontario, but if these really are cast aluminum, someone made them based on the production parts. This would be a lot of effort.

Even has the two-hole mounting boss for the heated air temp sensor used on the production part.
And, I'd be surprised if these parts weighed any less than the steel pieces. Why don't you check...

You need to get in touch with an old Dodge/Plymouth factory drag racer who was involved during the early '70s. How about someone from the Sox & Martin race team?"