well, that all depends on what you plan on doing and what you've got. we need more info. like what kind of t-case you've got, what you wanna do to/with the truck and so on.
for basics though to just swap a 12bolt or 10bolt for a corp14 you'll need a conversion u-joint for your rear yolk. this will be one of those things where you take the u-joint off of your old drive shaft and the corp14 and then ask them to get you one behind the counter that mixes both of them. NAPA is great at doin this stuff. then there's you rear drive shaft length. if you haven't lifted your truck you may find that its too long. so lift it or shorten the rear shaft.
hope this helps
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