I'm certain it wasn't the starter. The starter and that ignition switch have been peacefully coexisting for 40 years. It got new brushes and bushings but not within the past 8 years.
The HEI is current limited but not when it is energizing. When you first kick it on, it is flooded by 20 amps or more. In a bit I'll tell you why. There are questions and discussions like this on other forums (example found in about 3 seconds on Google):
https://www.chevytalk.org/fusionbb/showtopic.php?tid/188589/or even here at our forum:
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=408413&page=2And like any other subject you search for on the internet, you'll run across plenty of hooey.
If you want to run a relay (which I believe isn't a bad idea given you may have one of the old ignition switches) then run a wire from the "ign" post of the switch (will be 12 v positive) to one side of the relay coil and ground the other side. The pins on the relay will be 85 and 86. I believe most people use pin 85 for the ground pin. Then run a number 10 or 12 ga wire straight from the battery (most will advise against tying in at the starter where the cable connects but some people out there may have other thoughts on that) to pin 30 (I think I mis-typed that earlier) and then run another length of 10 or 12 ga wire from pin 87 (the normally open one) on the relay to the HEI coil connector. Your relay harness may have a wire connected to pin 87a. You can and should remove this as it is normally closed and will feed 12v through that wire to any convenient ground when the ignition is off. Wired correctly, when the coil energizes you'll get a large and healthy shot of electrons right straight in to it and it will be instantly ready. As long as the ignition is on, your HEI coil and distributor will be happy. These relays and harnesses are cheap, by the way. I bought a box of 5 on Amazon for less than $10 a year or so ago.
Now let's think about this whole HEI wiring scheme for just a bit. You say the HEI coil is limited to 5.5A. Yet when they began using the HEI, GM started using a pink 12 ga wire going to the coil. If the ampere needs of the GM HEI coil will be less than 6 amps and the wire isn't longer than 7 feet, it is generally accepted that 16 gauge wire is fine (up to 10 amps and this gives a cushion of nearly 50%). Why would GM spend the money on higher rated ignition switches and 12 ga wire? They wouldn't have without a good reason. If it would have worked, they would have made sure the harness wire to the coil was 7 feet or less and wired it with 16 ga wire and continued to use wimpy ignition switches and relays for things like A/C, cooling fans, horns, lights and any other high amp needs. But you won't find any instructions out there telling you to try to run your HEI on 16 gauge wire because of one fundamental flaw.
Wire that size will energize the coil but it is going to take a while. And the whole idea is to make the engine start quickly. If the engine takes a long time to start, people start taking cars back to the dealership for service. And without a fully energized coil, quick starts won't happen.
