Not getting 12 volts to coil

You're on the right track it sounds like

You have to "follow" the voltage through each terminal/ connector/ switch. The fact that you are using a hotter coil may be drawing more current than the stocker and causing further drop. CURRENT is what causes voltage drop through the RESISTANCE of the circuit. The resistance is ADDITAVE. Each terminal, each switch contact, each somewhat corroded wire crimp adds resistance and drop under load

Just follow the path. Man power goes to the IGNITION SWITCH CONNECTOR---through the CONNECTOR--through the SWITCH---back out the CONNECTOR and through the CONNECTOR--to the BULKHEAD CONNECTOR and through the BULKHEAD CONNECTOR and out to the harness and COIL

Each WORD is a place for drop. Think about the bulkhead connector. You have the brown IGN2 CRIMPED to the TERMINAL which mates with the enginge bay side TERMINAL, and that TERMINAL is CRIMPED to the brown wire in the engine bay. The wire then goes to the BALLEST CONNECTOR and is CRIMPED where it joins and continues to the COIL+ TERMINAL and is CRIMPED

Every single point there is a place where drop can occur.

You put the circuit under load (operating) and you check from the "high" (battery end) to the "low" (load end) and look for drop. Sometimes when you find "the big cause" it is WARM. or HOT. And there it is