5.2 magnum options

What do you mean, "a miss?"

What RPM, one cylinder, intermittent, stutter, etc etc etc Does engine load affect it?

have you looked over to make sure all the valve gear is intact, and that you don't have a flat lobe, etc?

You say you changed ignition, but WHAT ABOUT the supply VOLTAGE? Maybe you have voltage drop in the wiring TO the ignition.

Fuel supply? Pressure?

Way way WWWWAAAAAYYYYYYyyyyyyyyyyyyyyyyyyyyyyyy too many things left lying about here, before diving right into a major engine rebuild.