All e-body axles I've seen neck down right after the splines so there's not enough meat to shorten them. As Rklein said C-body axles can be shortened. Full size truck axles are also long enough to shorten.
This. Most B/E body 8 3/4 axles neck down slightly after the splines and stay that way through the area you'd need to put the new splines into. They do neck back up, but at that point they'd be too short for stock A body length.
C body and truck are the way to go for donors if you want to shorten a stock set.