Just bought a pair of rear axles complete with all parts from Porsche Main dealer here in UK. They were cheaper than all aftermarket suppliers I could find including some of your US ones previously mentioned (even without import taxes and shipping)
They are the correct fit, have the recess for gaskets and come with new roll pins which are real tight so give confidence on security when fitting.
OEM was the best way I found for price and quality
I also changed the bolt anti vibration washer/plates for peace of mind.
Best bit is they have nice glossy white Porsche "Genuine Porsche Part Quality" stickers around the shiny new shafts ;-)
Just like cuddyk's :-)
The reason Porsche main dealers can do them so cheap I found out when talking directly to the guys in Stuttgart who operate the Classic department when I visited them. They admitted Porsche hadn't reviewed the pricing structure for 914 parts in 20 years as it was low priority and low sales. Therefore any parts 914 specific are at 1996 prices, so go grab a deal at your main dealership while it lasts.
I spent a good hour talking with the classic guy's and Porsche are really waking up to supporting older models. There's lots going on to re introduce 356 parts back to main dealers shelves as we speak and the 914 should eventually follow. But its all about supply and demand, if we as owners don't walk through the main dealer door to ask or buy parts it ain't going to happen. This is a golden opportunity to get OEM parts back in manufacture and circulation.