For what it's worth I run a Hughes RPM AG with a 1/2" spacer, Edelbrock AFB and a '72 trap door air cleaner with no clearance issues. No insulation though.
NICE! I have a trap door air cleaner myself. Had two, sold one to Rani. It’s on my 5.9, in a ‘79 Magnum now on top of a RPM & Edel. 750. Good to know this stuff.
Do me (Us the forum) a favor and find some clay to put on top & around the outside diameter of the high points of the air cleaner.
Measure them up.
I’m not fond of using the drop base air cleaner on my wife’s ‘67 Cúda. I can’t remember the exact amount of clearance the MP ribbed flat lid has over the carb, but the closer it sits the worse air flow is going into the carb. So I trolled through Summit for the diameter and height of the filter to use and found one.