Well back on the Cuda after sitting a while cause of life interruptions . Car is 72 cuda with a 6.4 hemi and a 833 trans. Cat is going to have vintage air also. Holley prefers you mount the ECM inside car and cut a 2" hole in firewall. Wander if anyone has done this already and any pictures of install? Going to mount battery in stock location and make intake work. Also wandering where you mounted the fuel regulator ? What kind of fuel filter did you use? I ran stock fuel/return lines, and will adapt to hard pipe. Thanks for any inputs.

If want drop me an email
promano1958@gmail.com

Depends on the harness, I asked this same question with no response.
There's only 1 option for the Mopar harness, without completely redoing it.
Even with removing most of the tape, and rerouting, only spot available was right next to the AC box by gas pedal.
Harness just isn't long enough for any other spot inside car, without adding length.
Holley harness may be another story.
Another issue is whether the car has AC or not. Just not a lot of room.

I removed the air inlet door assembly, (above the parking brake pedal)
I made a plexiglass block off and mounted my MSD 6AL to it.
I hope this helps

on my 70 E-Body I placed it passenger side interior under the glove box. Mine is a FAST ECU though, I had plenty of wiring to place it within the interior.