NOT AN AD, just info. When Gene and I built his MSD Trigger only conversion, I also built him a stand alone totally remote HEI setup, with HEI module and input/output/ground wires, with alligator clips on their ends. This allowed Gene to use a real world timing light, and no dial back when he wanted to set, alter the timing in the system, then go back to the MSD when he was done with it.
For me, serviceability is essential, the more versatility, the better.
Later on, it donned in my ancheint, old fart backfire head that this setup could be made as a stand alone setup for any of my MSD Trigger Only conversions, if someone wanted to go back, to an HEI from an MSD, simple. There is a picture of what I came up with on the website, but that one doesn't have the alligator clips to temporarily attach it.
As far as any HEI COIL, I am a firm believer, from decades of hands on experiences, that the remote mounted, oil filled round coils are the best to use. From way too many HEI module failures with the epoxy coils in the caps gong bad, slowly causing both their, and module failures, I use the oil filled coils, and the module failure issues virtually stopping when the in cap epoxy coils are changed out. I have a 1986 GMC Safari with 4.3 V6 and factory 5 speed. It used to take an EFI HEI module and coil out every year, just stops dead on the road. In 2010, I had a module and coil fail, and replaced the EFI-HEI module with the same standard one I had always used, and the coil with one of them I use, oil filled round, for my small-body conversions. This van is used for a senior citizen's food program, it carries the canopies, tables, facilities for distribution, is my pickup truck, and goes about 30K per year, and it hasn't farted, belched, hiccuped in all these last almost 10 years. It even gets better fuel mileage than the old epoxy coil did.