318 Running Rough / Backfiring

74Dart318 said

Fuel pressure jumps around between 5&7 psi

I'll have to pull the plugs

Backfire through exhaust

Click to expand...

Popping, burnt exh valve...but backfire is loading up unburnt fuel with heat setting it off down the line.
What fuel pump are you using?
It is possible you run champion plugs and an insuator came lose, it is misfiring.