327 randomly runs bad

['63MurderTruck]

My son's truck is 'randomly' running bad...

It will be running along just fine, then out of no where start running horrible, then... out of nowhere it starts running fine again.

Also, the 'idle' is all over the place. One second it will be at 1500, then drop to 1100, then down to 800 where it is SUPPOSED to be, hit the gas again, and back up to 1500 RPM. Weird.

I thought it was a FUEL issue, so... I've put on a new carb Edelbrock 1406, new fuel filter, and new fuel pump(mechanical), and it still does the EXACT same thing. It has a full tank of 100% gas from the same station that I always get it.

Now I'm thinking maybe the HEI distributor, which is also BRAND NEW. Any ideas what else could be causing this?

This is basically a stock 327 with an aluminum intake, Edelbrock carb, and headers.