[swamp rat]

On a stock setup (should be the same with the HEI) there is a lead coming off the switch that will be hot when the key is on the ON position, locate that wire ether under the hood OR just remove the switch from the dash and test it there, turn the switch to ON, then jiggle the switch and see if the light go's out or flashes intermittently, if it does get a switch.

Make sure the PO did use fuel line from the tank to the pump, I have seen cases where non fuel rubber line was used and it was ok at first but it would soften then the vacuum created would collapse the hose.