The obvious options are;
1: Defective fuel pump. You say its new so not likly the issue
2: Carb running horibly rich, you say the plugs are tan so not likly the issue
3: Leak at the intake gasket, you would also have erratic idle and oil consumption
4: Carb leaking gas into the manifold when the engine is shut off, it runs down into the combustion chambers and runs past the rings. With 1-3 95% eleiminated I say its time to start looking at this used carb. Some will say run the engine until its hot, shut it off and look into the carb and watch for gas drips. Only problem is its likly you will not see any and think your good to go when the problem is right there so first I would look at fuel pressure. Holley makes a nice pressure regulator for abt $40, has 3 1/4NPT fittings (1 in, 2 out). Plumb that in with a gauge and set it. What ever I sugest will start a debate, I want mine to run impecable and am never on the throttle more than a couple seconds so I set it at 5, 7 would probubly be fine for a Holley, If your spending the day at the drags you might go higher.
If that does not fix it you need to get into the needle & seat & float level area.