Mopar electronic conversion fires 4 cylinder only

I kind of thought the rocker shaft worked its self loose, but if there is truly no spark then it wouldn't matter. You say it turns over smoothly, and a shaft that worked loose may not allow that. There aren't a whole lot of things that the cylinders of one bank have in common. Crank, head, rocker shaft, cam, and rocker cover is about it. Unless an ignition problem is clearly obvious, I start with cap and rotor always. I did have a Demon that fired very strangely,but it had a bent dizzy shaft. Maybe the dizzy has a bad bearing.