Get an old Mopar ECU, which color is irrelevant. Torch or scoop the silicon jelly out of it and rip most of the circuitboard out, except for the connector and pins on the inside.
Install/fix a 4-pin HEI module inside and wire it to the original connector pins.
Make sure the HEI module connects properly (use heat paste) to the aluminium cooling unit.
Discard ballast resistor, retime distributor and drive off.


Or looky here;
https://www.forabodiesonly.com/mopar/threads/hei-in-mopar-ecu-casing.252705/