It's possibly a bit late in the day to post this but, in no particular order, why are you fitting another coil? Is the old one bad, is it an ignition lock/key problem maybe? What do you think you will gain from the change? Fitting Pertronix?
They rarely fail, although I admit they're not getting any younger. If it is still good I'd try and take it out as a complete unit and use an aftermarket ignition switch with your new coil. The armoured types are very sellable if they are good and undamaged.