is this a 2wheel drive, if it is any gear ratio will work, its simply a swapping of gears,
if its a 4x4 you must ensure your rear pot gear ratio matches that of your front pot "diff".
There is a previous post I answered to called "rear end", it states where to find
your rear end information and what the codes in your glove box mean
and I think they differentiate the rear ends for our years of trucks by the number of bolts that hold on the rear differential cover not its diameter. It should be a 10bolt or you have the size of 8.5" correct
One recommendation, pull off the differential cover and make sure its a limited slip not a full slip,
limited is by far more desirable unless you want to drag it then you want a non slip.
full slip = if one rear tire slip spins the other is a dud and just sits there
limited slip = if one tire starts to slip spin the second tire will be actuated and begin to spin,
perhaps getting you unstuck or giving you more traction