Well, FWIW, the answer to my question is the following:
This is a NAPCO axle manufactured by Dana for IH. It's rated at 9000 lbs and tips the scales, with hubs and brakes attached but no wheels, at 1260 lbs.
I think Cornbinder89 got it right as it's referred to as a S-9000 because it was made for the S series of medium duty IH trucks of the early 80's and is rated at 9000 lbs. (In contrast a heavy duty Dana 70 as used in the IH Loadstars is rated at 6000 lbs.)
Although the pumpkin assembly seems to be interchangeable with a RA-30, the axle assembly is actually a FA-64 or FA-78 with a corresponding IH code of either 02064 or 02078. I have not been able to find any difference between the two in the IH parts books, other than possibly the brakes.
Most parts are still available either directly from Dana or from IH/Navistar at three times the price of the Dana equivalent parts.
I've found the parts breakdown in two different IH parts manuals (MT-140 and MT-145), and the servicing of the axle assembly is in two different IH shop manuals and at least 4 different DOD military service manuals.
BTW I have the military service manuals for this axle assembly and for my Rockwell transfer case and I've found the military service manuals to be far, far superior to the IH shop service manuals. If something is not clear in your IH shop repair manual you may want to try and find a military service manual that covers the same topic. They may cover the same things but are much more detailed in their procedures, pictures, torque specs, etc. and seem to be geared toward the person with little experience.
What I find interesting is that both the IH parts books and Dana tech support refer to this as a NAPCO axle. NAPCO was one of the original leaders in converting trucks to 4wd until the mid 50's when the big three manufacturers began offering their own factory 4wd systems. According to NAPCO's web site, they still offer parts support for military trucks and tanks, including the less common vehicles of WWII such as the M2/M3 Half-Tracks etc.
http://www.napcointl.com/about.php I have yet to contact them to find out if they offer parts support for this axle too.
I could go into a lot more details on this axle assembly, but not much point unless you're rebuilding one.
Thank you ibesq, nikkinutshop and especially cornbinder89 for your replies. Your comments and help is appreciated. Thank you, gentlemen.