mufflers or no mufflers??

Here are my thoughts.

510 lift cam with 273-318 manifolds. Not good,will run out of breath quick.

Was the cam degreed?

Like the flowmaster's.....Straight exhaust,Not good.

5/16" fuel line....3/8" would be much better.

MSD boxes can be as much a headache as they are worth.
Factory Mopar Performance electronic ignition works fine for a street car.