Thanks to all of you for taking the time to share your experience.

As nice as a dedicated oven would be in my garage, I'm saving that circuit for an air compressor, so heating the Air cleaner will have to be done with shop lights as suggested, or maybe hanging it in front of the garage furnace while it's blasting away will work.

It wouldn't be up to the standards most of you have for parts on your ride, but the system I'm doing is just a stock '73 2-bbl air cleaner housing "morphed" with the finned MP open-element air cleaner, and fed by home HVAC ducting from the cowl.



To combine the lids, The finned MP piece remains unaltered. I cut the raised center section (red arrow, below) out of the middle of the stock lid.



Then I made cuts in the remaining section and bent it down flat.
(See "doctored" pics below)This still provides plenty of support strength, and allows the MP lid to sit flush (except fins) inside the outer flange.



The outer section (red arrow, below)) of the MP base was cut off, and the remaining center section replaces the one cut out of the 2-bbl. base. The 2-bbl. base has cuts in the remaining outer section,(like the lid) but the "tabs" have been bent upward to match the curve of the MP center, which sit on top of them.




It may seem like a lot of work just for a "pretty" air cleaner but the "engine compartment" of an old Dodge van is a liitle sweat-lodge on steroids, and just isn't friendly to an open element air cleaner. Total investment so far, is $50.72 with most of that($40.63) going towards a K&N stock replacement filter (for a '75-76 Mustang II w/V8) Hopefully, the finished system won't total for much more than $100.
The 2-bbl. base has cuts in the remaining outer section,(like the lid) but the "tabs" have been bent upward to match the curve of the MP center, which sit on top of them.