Popping & Banging Under Heavier Throttle...

[Ford Assassin]

Hey guys I recently picked up a '69 C10 SWB for a little truck project that me and the better half can do together.

Anyway, it has a late '70's 350 engine in it (junkyard special I am sure) and it idles and drives normal very smooth. However, anytime I get into the throttle past half way and the engine speed goes up it starts missing and popping/banging through the exhaust. I can feel the loss of power as well.

Its got a HEI distributor already, but I went ahead and changed the cap, coil, rotor, plugs, wires, etc. and I played with the timing (10* initial). I also swapped the carb out for another one and still nothing has improved. I haven't pulled any valve covers yet, but I don't hear any unusual valvetrain noise.

Ideas?

Thanks guys!!