[jagrolet]

ed
one thing that i have found years ago, is that most pumps,(electrical or mech) do not draw fuel very well from below their level.Basically,most electric pumps are "pushers" not "pullers".

In 1972 i had the same situation with a 66 bb vette,the hot ticket at the time was ac delco industrial strenth electric pumps. After a bunch of head scracthing and pump replacing,the pump was put as low as possible with the scrub line of the tank,and with no upward motion of the infeed line to the pump.
I sure wish i could remember that part number,it may have been in the motion hand book.

Also,check (if running carbs) manf"s recomended fuel pressure to needle seat. This is one of the major mistakes people make with holleys (it results in all kinds of mayhem). And what gives alot of holleys a bad rap.