Ralphy,
Wasn't a 50's (& up) GM car that used a ballast resistor at/to the coil but a 72 VW Bus! VW couldn't find it and neither did I! Like Ray says, OEM? To Hell with OEM, I want it to work!
I did what you described only instead of having to get out of the Van, go to the engine compartment hook, unhook the extra wiring, I simply 'hard-wired' the extra hot wire in place and put a toggle switch on the dash to either break or make the circuit! That problem was fixed, maybe not repaired, but it WAS fixed!
Sunman, I love soldering in floor pans, and 1/4 panels in vintage Mustangs-I really do!
(You should see some of the floor/trunk pans I have made by hand with all build in valleys, pockets., ridges, and these were for a Kennedy Lincoln, '57 Chevy's, '56 Chevy's and on and on! Now you can buy complete pans already with the factory stampings in place!
DV
Sunman, I will do exactly as you say once the guy gets his/the car here!