If you think it's a timing problem I would be tempted to adjust the timing up or down with the engine running until the surge goes away. (If you can get it to surge without driving it) Kinda' like timing it by ear. I'm sure an old tune-up mechanic with a scope could hook it up and tell you whether you have a bad
control box or other component. Without some diagnostics, you have to replace components until the problem is fixed. (like you did with the carb). Is there any older Mopar techs out there that may have run into these symptoms before.
Usually surging is caused by a lean condition and by switching carbs may not change much. Did you suck a intake gasket in? Spray a little carb spray around the base of the intake with the engine running and listen for a change in the way the engine runs. Just some suggestions. Good luck and keep us posted.
toolmanmike
