If it's a 12 bolt truck diff, then yes, it'll work. But you'll need to be looking for no later than about '77. GM went to the 10 bolt after '78 for most 1/2 tons. Also, be wary of pre '63-'65 diffs, they use a different spline (17 instead of 30) with a mid year change in '65. If you truly want a Posi, check out the aftermarket. Lots of choices available, new, plus gears if you want to change the ratio.
