I have a leak at the back of my 518 transmission. Looks to be where the u joint goes into the tail shaft. The car is a 72 cuda that I bought last year. Want to make sure I get the correct seal. Checking on line, not sure exactly what year the trans is, think 1990 -2003. Anyway to tell for sure? or get the one for 1990-2003 and newer version thru 2012 One at Class transmissions SKU 5697 for a A518-A618 IS 2.507 IN wide. Summit shows a 5086341aa for 2003 to 2012 years.