I have a A-500 automatic with a 4th gear lock up, bought the 72 cuda with it. Had a leak, pulled the pan, had a hard time finding the correct filter, think I have, wix 58656, fram 1015a, Got a good gasket from the dealer, but can't decide on what fluid I should use. Bought ATF4 but have seen info that says dextron 6 is what I need. Can I use ATF4? Need help, thank you.