I have modified LD340 intakes for thermoquad use. They can be done nicely. It really helps to be skilled with a die grinder and it takes more time than most think. I've looked at perf RPM intakes with the intent of modifying for a thermoquad and concluded it could not be done without adding an adapter (to an already tall intake) or extensive welding.

Note: No aftermarket intakes that I have measured have as low a profile as an LD340. Going from memory, they are about 5/8-3/4 inch shorter than a perf rpm or weiand action.