When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I've heard good and bad over on the HAMB. I would avoid anything but a stretched OEM axle, personally. There are two outfits that do it right and reliably, I think one is in OK and the other in AZ. Do some web searching I'm sure you'll find them.
OK, I found it, pg 98 in my 2012 catalog. The assembled axles have a reputation for the ends not being in alignment with each other, likely due to warpage in welding. The link in 49er's post has an excellent reputation for building accurate stock width dropped axles and they are cheaper than the Speedway ones.
Stretched means they literally heat the end of the axle and stretch it to produce a drop. Some companies make brand new axles that incorporate a drop, but the metallurgy and manufacturing methods are frequently suspect. Ford used very high quality steel of the proper alloys, and huge forging presses. Many of the aftermarket (new) axles are cast iron, which is brittle, but cheap.
Some droppers simply heat the axle ends an rebend them to produce the drop, but when you do it that way the kingpins move in towards each other making the tread width narrower. By hammering (forging) the hot steel you can stretch it to compensate for the tighter bends so the axle remains the same width as OEM. The Axle in question that Speedway sells is made from CNC milled steel billet axle ends that are inserted and welded into a steel tube center. Some that bought the 3 piece axles found that the king pins were not aligned with each other. It was generally thought that even though the axles were welded in a jig, some warped and twisted as they cooled or as the spring perches were welded on.