ok, how di know what I have? i looked at it when i was under thecar to remove the tank. did notmeasure it though. 1970 swinger mnual brakes, 318/904..........what is the visual diff between 7 1/4 and 8 1/4? I belive the 8 3/4 kinda looks like a ford 9 inch with the thrid member installing from the front of the axle and a solid housing.........right????? can someone post a picture on here for me???? please