[FC] differential question

[Phil]

have a question about differentials,maybe someone can help,iam going to put in 355 gears,what diff is better to use,1960 diff  1961-1964 diff 0r 1965-1969,and why should I use it,i know the 60 diff has two short yokes,and the others have one short and one long,can someone tell me why the 60 is the only one with two short yokes,and why did thay change to one long,thanks for info...