Jack, I'd go with the GAC 7, for three reasons:
1. It is sonically superior to the GAC 4
2. Not sure where you get the necessary fifth conductor from in a four conductor tube mic cable like the GAC 4, unless you use only the cable shield als ground
3. Cost difference between GAC 7 and GAC 4 is marginal, especially considering the overall value of the mic system. That's like mounting some Cheng Shins on your Porsche, instead of Michelins.
RE: terminating the GAC 7:
I would use the traditional European tube mic cable colors, first established when everyone was using Austrian Doerfler cables, of which the Gotham GAC 7 is a direct successor:
Audio (+) = white
Audio (-) = brown
Heater = Red (thick)
Ground = Blue (thick)
Yellow = B+
For complete RF protection, make sure to connect the cable's ground and shield on both connectors to their respective ground pins, and the housing lugs of the connectors!!!
