I'm keeping everything stock on the new engine/ trans. and keeping the rubber the stock size all the way round.
Ford 200 I6 cars came with a 71/4" rear end from 1960-1969 ( 8" after ), and the 250 cars came with a 8" or an odd 8.8" in 1978-1979 in some Mercury's. 1 of my other cars is a '67 Falcon 6cyl but I'v never changed the U joint on it... Didn't know they used the same joint as the Rambler