Overlooking something? Fuel Starvation
Had a problem like that once. Everything was OK until I changed to a steeper rear gear (3.23 to 3.91). Swapped the 650 Holley for a 750 and the problem went away. For some reason 318's like to be over carbed, at least when they have vacuum secondaries. Never tried a double pumper that size so I can't say how it would work.