Sounds to me like you're putting a '97 Chevy engine/trans/t-case into your '72 Blazer and need a driver's drop front axle but want to stay 6-lug.

Ball joint 70's/80's D44's are basically all the same on the inner knuckle. You can bolt Chevy outers onto a Ford 44 and vice versa.
Like you said, use the Ford inner shafts that match the housing width and the Chevy outers that match those knuckles/spindles.
The Chevy 44 diff parts will fit in the Ford 44 housing as well, as long as they are both low-pinion.

The only thing you may run into is that your '72 Blazer axle probably has the older, smaller u-joints. I'd recommend using shafts that use the later, bigger ones.

My front axle was out of a '72 blazer too, and I upgraded the shafts (first bigger stockers, later chromoly).