question for the diff experts

[casey]

my son bought two diffs for his 77 ford 4x4, for 150.00 there 410's, heres the confusion for me the rear is 37 crown 9 pinion=4.11111111 the front is 45 crown 11 pinion=4.090909 does it matter if there not exactly the same ratio, i was going to put the rear diff together myself cause the gears come out assembled, just have to pull the axels, it looks like it a limited slip or posi, how can I tell, one more question how do you change axel and pinion seals, thanks for the help