Is there a difference between the 00R and the 03/04 units? If there is, it might be in spline count? The 01 and 03/04 shafts are 31s inner and 28s outer...99 Cobra is 28/28. Or is the inner stub different due to the viscous coupling differential?
There are plenty of 03/04 shafts out there, if they will fit...
Aha...answered my own question. If you're intent on keeping the Gerodisc, you'll likely have to have that axle rebuilt unless you know the GKN part number:
I have a new (unused) Gerodisc differential for the Cobra 2000 R (there were 305 units manufactured - this is 1 of the 5 made that were not put into cars). If anyone is interested I can e-mail pictures / discuss price. I was going to put it in my '3 cobra, but then found out that it required...