Jack,
Try checking the firing order of your plug wires. 13726548
Also popping back trough the carb is an intake being left open at the wrong time, check the valve adjustments.
Set the timing with the vacuum advance hose off and plugged.
When all else fails, try advancing the distributor while engine is idling, move it clockwise 1/4 to 1/2 inch, if this helps then your harmonic balancer may be out of whack and need to be replaced.
Good Luck,
Perry.
