My heavy 408-powered rig with the 39.5 IROKS has been routinely shredding D44 front axle shafts for years now. Wishing I had gone with a 60 up front aside...I recently bought a set of the RCVs but have not been able to put them to the test yet.
I also have everything to convert my '78 Bronco on 38s to 1-tons..having given up on the 44 in the front of that for the same reason; the 408 snapped any brand front axle like a twig. Never hurt the rear 9" though...and it with "only" 31-spline aftermarket axles.