you are correct in your first post
pin 6 is solenoid bus 43VDC= blue/white tracer
pin 7 is feature lamp bus 5.4VDC = blue
your new rectifier board will most likely come with J1 having 9 pins.
your call whether to use a new 8 or 9 pin connector housing?
either way pin 4 is your keying plug.
the white wire may be your AC return but easier to tell for sure with a pic to see where it is soldered to, won't matter as nothing is soldered to the back and you'll be starting anew.