Car: 1976 Charger Daytona, 360ci.

Issue: I have an electric in-tank fuel pump instead of the engine-driven pump assembly...prep for an eventual engine swap to a Magnum 360 on Holley Terminator X. When running, this pump is more than enough for a stock 360 (350 LPH). The problem is just that...when it is running. I'm finding that this pump cuts in and out at random times. It has been very difficult to diagnose. The pump has a power wire from Battery Positive and is grounded at both the front passenger fender ground and at one of the two fuel fill tube bolts inside of the trunk. I'm suspecting key-on 12v power is my issue. Right now, that is sourced from the electric choke connector (CE 14 per the book) because that was the only actual point of key-on 12v power I could locate. When the car is colder and as long as it doesn't drive too far or too hard, it's fine. But drive it hard, or try to take a roadtrip and eventually the car will choke out like the alternator died and the battery went flat. Let it sit a few minutes, it'll start up and move.

In preparation of the new engine, trans and ECU, I'm looking to see if there's a better key-on 12V source under the hood I can use instead of the choke's power supply. I was looking at the starter relay for a minute, but I only see 12v hot at the top terminal, 12V to solenoid for cranking and 12v ignition. I do not want to put a hard-mounted switch into this car. Am I missing any other key-on 12v sources?