[Mike C]

I see the one picture of the side of the truck. Sure the truck is not a 69? It would have had closed knuckles. 70 is an open knuckle drum brake truck and you can swap the knuckles from a later 44 along with the discs and axle shafts.

You said this is a shortbed truck? If so it should have the 12 bolt rear and the 44 front. Obviously the easiest is to find a 71-72 donor for both axles. Any of the 71-87 front axles will bolt in, perch and shock mount work needed on the 73 and up rear axles. Dana 44 up until around 78-79 and corporate 10 bolt until 87. 91 in the Suburban and the Blazer.

If all you want are discs, grab a 6 lug disc front from any year that has the same gear ratio that your truck currently has in the rear.

Please supply some pictures of the front and rear differentials as well as the knuckles on the front so we can better identify.