SC shafts are larger diameter bars, MArkVIII have a hardened outboard joint flange and spline.
Thank you Alan for your insight.
I was on the phone today with NAPA and ask to cross reference new half shafts for the n/a 3.8, 4.6 liter, SC's and Mark VIII's.
All carry the same part number 10070N. Same with rebuilt units: part number 8379.
Interesting too that NAPA said that even though they have a part number for new half shafts they are unavailable. Could perhaps be special ordered. Cost of a rebuilt unit is $60.00ea. with a $20.00 core. Gave me a tech support number to Cardone. The OEM company that suppies the h. shafts. 1 888 280 8324.
The support tech at Cardone said they do not manufacture new half shafts. Only rebuild used ones. Again all are the same part number regardless of application.
Went on to inquire about orignal haft shafts that were installed on these cars upon assembly. Said he wasn't sure. We both agreed that perhaps OEM companys decided to save money by lumping them all together instead of four different units.
So now what I will do is with a VIN from all four cars (n/a 3.8, 4.6, SC, and Mark VIII) ask my local Ford dealer to look up the different half shaft applications.
"Strange" told me they do not supply any half shafts for these cars. Nor are there any plans to do so in the future.
Bill at SCP told me if you have a V8 it is the same as an SC.
What all this tells me is that if I pull the half shafts from an SC or Mark VIII at the bone yard it doesn't necessarily mean it is any stronger than than the two on my 4.6 Bird. After 15+ yrs. of service it could be any one of the four half shafts. Perhaps even a combonation of rebuilt parts.
One could Max Cal the "bars" and make an educated visual inspection of hardened componets.
My goal here is to document specific part numbers stamped on the half shafts themselves to know for sure, and post those results here for fellow club members.