Back in 1966 I offered to pay for a 8.75 limited slip diff in my 65 Dart 273-4 if my 5-50 warranty would be retained. Factory service rep said no. Any change from factory drivetrain equipment would void warranty. Seemed silly to the dealer service manager at Chuck Hutton Dodge in Columbus, GA. The factory would rather pay to replace spider gears in my 7.25 than warranty the 8.75 I paid for.
Might just have been that particular zone service rep, but that was his decision or the factory, I don't know.
