440 power gains/ aluminum head advantages?

factory style mech fuel pump
THAT imo is your problem, probably still have stock 5/16” line too. 3/8” aluminum line minimum with electric pump. The Red Holly street pump will work fine in 1/8 mile, a blue in 1/4. That 850 DP is running out of fuel! Also unless your tank is full the gas is moving away from the stock pickup