HH56 wrote:
Quote:

'55 was + grd. and '56 was - grd.

True but the way the starter field coils and armature are internally connected if a change in polarity occurs both items also change at the same time so the magnetic relationship and rotation direction stays the same. Generators and ammeters do care as they typically need repolarizing and reversing connections on the ammeter before they will charge or read properly after a polarity swap. Regulators are another item that might care and coils work better with a change of connections to match polarity but will still work if left alone.

As a point of information as evidenced by all the accidental or sometimes on purpose changing of pre 56 cars to negative ground to accommodate modern radios or cell phones, starters and other electric motors Packard used as an original part do not care about polarity.