You will get good advice here on this forum, but the other component you asked for was wrecking yards. Good advice will rise to the level of what vendor made the axle, and what machine shop to use, and what vendor sells the u-joint spiders and hardward.
You most certainly will not find a Ford 4wd tractor axle in a US wrecking yard. I have, though seen axles listed in Britian.
I have one of these axles on my tractor, as stated and I have chased this gopher down the hole more than once. Mine wasn't broke, I was mainly trying to help another guy with his axle. I have had my hopes raised by those who said they could help, only to wait and get more rhetoric. I have contacted people in Britian, and I learned that if I used the forum I gave you, I could find a guy on the ground there who could point me to a Britian whose dad made these conversions, etc and I could get parts.
BTW, I routinely order parts from Britian, they will get here.
Bottom line. Great friends and good advice on YTMAG. Seems like you need an advocate in Britian to find a part in a wrecking yard.
Just my 2 pennies of advice.