S13 SR CAS grinding/squealing? W/video

[FleetRunner]

I'm finally getting around to getting my s-chassis project out of the back of my shop, I've got it up and running but am running into a noise in the front end I can't seem to figure out. The noise happens after the engine is warmed up and seems to be coming from the front of the engine. I've removed the power steering belt and inspected the alt, wp, and crank pulleys to eliminate them as options, but the noise appears to be coming from the front of the head. Today I removed the valve cover and took a decent look, it appeared the cam angle sensor hadn't been lined up properly last time it was installed and there seemed to be a bit of polishing on the tip of the shaft where it sits in the head. Aside from that, the CAS spun freely and nothing jumped out at me. I cleaned and greased the shaft and reinstalled the CAS with proper alignment, the engine runs much smoother, but that darn noise is still there.
Video of the noise: http://youtu.be/KYxEM2UQVPg

My next step is to pull the valve cover again tomorrow evening, ensure my oil squirters are working, and swap the CAS for a second one I have sitting around... I have no idea what condition the spare CAS in in, it doesn't spin quite as freely as the one that's in there right now and there's a little noise to its movement, but at this point I'm just curious to see if the sound will change any. Beyond that, I'm pretty much stumped. At the moment, nobody I have asked has another spare CAS laying around. By any chance is this part shared with other cars, or is this gonna be an expensive one if it needs to be replaced?

Thanks in advance!

[FleetRunner]

Tried swapping in my spare CAS with no luck. It was nice and silent for about 10 minutes, but then once everything got nice and warmed up the noise came back. I can feel the vibration through the CAS cap, and the noise changes when I play with the timing adjustment at the CAS. At this point, I'm starting to think I have two functioning sensors with bum bearings... my buddy has access to all sorts of bearings through his work, so the thought of disassembling one of my sensors and replacing the bearings has come to mind if that is in any way possible (money's a little tight ATM).
While I was under the hood I gave everything a good second once over, and nothing jumped out at me. I snapped a couple pictures in case more experienced eyes might spot something I missed, though.

Overview w/sensor installed


Gear mesh looks clean on both sides


Looking through the CAS mounting hole to where the shaft sits in the head. I originally thought the noise may have been coming from that area, but there just isn't enough wear showing IMO.


Any ideas? Any clue where to find a new or rebuilt CAS for less than $350?