I just did a rear end swap on my Galaxie.  I went from the 3.00:1 pumpkin that came in the car to a 3.50:1 unit.  When I bought it I was looking for a ford 9" with lower gears AND a long yoke so that it would be a simple swap.  Turns out not as simple as I hoped.  As I was putting it all back together today I went to install the driveline and I discovered the u-joint was not big enough.  I found out Ford had two standard u-joint one for normal use 1310 (which is the one that my galaxie came with) and one for heavy duty use 1330 (which my new rear end required).  The two two u-joints are almost identical including cup size however the "heavy duty" u-joint is about 1/4" wider when you measure from the end of one cup to the other.  Good news is they make a 1310 to 1330 conversion u-joint. The Moog and Percussion part # is the same, part # 235 and it is no more expensive than any other u-joint.  My local Napa did not have one neither did my local O'Rilly's, but Autozone carried it in stock part # 1-0134DG