I thought You were using a engine cooling fan, heater blowers can run on 15 amps. Buses are wired with 15 amp breakers and 16 gauge wire up to 15 feet long. I changed out a ton of 15 amp circuit breaks because they kept overheating with heaters on high speed till we found the manufacturer uses a janky ground terminal hidden in the wall. Once we fixed the grounds, dual blower motors would run on 15 amps all day long.
HEI will run just fine with a little more or less amps then you think. We have always just wired them into the ignition switches with no thought given about amp draw. Since the early 80's I have been installing HEI to standard ignition switches with no problems. I am not sure what HEI and overdrive have to do with each other, so please show the link or explain that one.
