Will,
I sent you a PM.
I have Wilwoods as well. I removed my hub assembly (a couple of seasons ago) to have the front right rotor trued up.
The part in your photo is the Inner Front Wheel Bearing Shield. I made sure I replaced it. It helps keep the grease from seaping out of the inner bearing race (ie.helps keeps grease in the race). The part is just inside of the end seal (with the rubber lip). The end seal keeps the grease from coming out of the hub assembly.
The part is available from Wilkinson's - I'm pretty sure.
Can't tell you what caused the failure - my guess would be too tight a torque on the hub installation. However, (I know you are quite mechanically inclined) here are some suggestions.
1) You may have metal bits in the hub assembly as a result of the failure. If you get the rotors machined (trued up) you most certainly will have metal shavings in there. Make sure you clean the hub out to the point where you can eat off it. Then re-grease with fresh bearing grease. As you know bearings like clean grease.
2) When re-installing the hub make sure your re-installation follows the factory guidance to the letter. You know, tighten the nut (inch-lb torque wrench to torque) while spinning the hub. Repeat a few times. Then put the cotter pin in etc.
Yours,
B.G.
P.S. Your car is a beauty. Please reply to my PM
