Either the ignition switch is bad or you have it wired incorrectly, or the wiring has generated a problem
There are TWO switched ignition sources, IGN1 and IGN2 off the ignition switch. IGN1 is "run" BUT GOES DEAD during cranking. IGN2 is hot ONLY in carnking and feeds ONLY the coil + side of the ignition
When you run something like HEI with no ballast resistor you must tie them together
Problems can be in the bulkhead connector, the ignition switch connector, or the switch itself, or of course a wiring mistake
Since you have made this modification the most logical problem is that you did not get thet two wired together
