Rear axle swap (7 1/4 to 8 3/4) - driveshaft?

Factory shafts differed by 2.03" between the 7.25 and 8.75 rears, all else being equal; but double check that when you mock it up before you have yours cut. Also check your pinion yoke on the 8.75 to make sure it takes the same u-joint as your current shaft, so you know whether you'll have to run an adapter u-joint or just have a different (compatible) end installed when your shaft is cut; your choice on that.