71 Dodge Dart Swinger in England

I like your wing nutted HEI setup with home made mount plate. The HEI helps with faster starting. Swap W and G leads and see if that corrects your engine miss issue. Also did you get rid of the ballast resistor and connect the 2 ballast resistor wires together? HEI modules need a good 12v signal not 6V like the mopar unit. You may have a pickup module going out so getting one from "the rock" may help. They arent too terribly expensive. If thats not the issue at least you have a spare.