Does your car still have the original mechanical voltage regulator?
Will the voltage increase if you speed the RPM up?
Me thinks you may have continuity issues now on the firewall gang connector after moving the main under dash wiring harness around
There is no magic in wiring with electricity , it is either connected good, not so good or bad
BTW, it took me quite a while to figure that out working for the telephone company 33 yrs, I retired long time ago in 1996