HEI conversion benefits

Easiest and cheapest is the Ningbo "ready to run" distributor on ebay. I put one on my 1965 Dart 273 ($45) with the e-core coil ($20) (both from seller Steve White Performance). Not avail for slant-six. I also found a spare module ($15 ebay), which I think is used in some Japanese cars. Prices may have increased (despite assurance of "no inflation" from U.S. President a few years ago).

If you already have a Mopar e-distributor, perhaps better is the GM 8-pin module and coil, shown in post 10. I am probably the first to suggest it here (upset SSD since he had only heard of the 4-pin module), but not my idea since found it and much more ignition info on the megasquirt site. One advantage is that some aftermarket EFI kits can command spark advance to the 8-pin module, such as the Holley Commander 950 on my 1965 Newport 383. I pulled off a 1985-95 GM truck at the salvage yard cheap.

Or you can spend more time wiring the GM 4-pin module and have exposed spade connectors, rather than the sealed Metri-pak connectors of the 8-pin module. If you want to spend $$$, there are many aftermarket ignition kits for ~$500 from 'merican companies.