Yes it is 51" from center to center of u joints. Yes it was balanced at the driveshaft shop that built it. Yes I take PayPal. The rear Ford u joint has 2 sizes. The part of the u joint that connects to the yoke is the small size and the part of the u joint that is installed in the driveshaft is one size bigger. I am currently out of the state where my parts are located so I can't give you a measurement. Someone with some Ford knowledge probably knows. It is slightly smaller than a Mopar 7260 small yoke.