318 Engine stumble

I had a similar issue, 74 Duster, mild built 318, stock electronic distributor, Pertronix flamethrower HEI modue and Pertronix flamethrower coil. Bought motor carb to pan from a 3rd party who took the intake off to photograph the motor to sell it showing assembly lube on the cam etc. Turns out they never re sealed the front and back of the intake with new RTV, just tightened the bolts.
the motor fell on its face about 1500 to 1700 then smoothed out. I had a leaky brake booster so the motor sucked air thru the vacuum port. Fixed that then had 18" vacuum, but a wicked oil leak then showed up with motor running. Took the manifold off and discovered bolts were super loose and RTV was not sealing. Got new fel-pro caskets and re sealed water jackets and corners and 2 small beads on top and bottom of front and back cork gaskets. Going to put it back together and I hope I have no leaks and it runs as it should. I look forward to hearing what happens with this poster...