Classic/Antique Car Repair: 1955 plymouth charging system, 1955 plymouth belvedere, mechanic friend

Question
Trying to help a friend with a 1955 Plymouth Belvedere.  The car stopped running and a "mechanic" friend brought her an 8 volt battery. The car started and ran fine until it stalled at a recent cruise. The battery was dead.  Obviously I am going to replace the battery with a new 6 volt.  I tested the generator  per the manual and seems to working fine, yet with the engine running if I disconnect the battery it stops.  My question is:
Would the 8 volt battery have burned out the voltage regulator or do you think this may have been or is the problem now?
Thanking you in advance.
Scott

Answer
It is possible that the 8 volt battery hurt the voltage regulator or I would guess that the regulator failed and that is why the jump start was needed. Now if you have tested the generator by jumping the field and it charges that points to the voltage regulator and that is the only on car test for the VR. But all points to the VR that is if all the wiring is intact.