So I finally took the time yesterday to sit down and address the grooved clutch basket.
I was trying to figure out a way to utilize a grinder, or Dremel to work most effectively, but in the end there is no replacement for the flatness and accuracy of a handtool.
Bench Setup, was able to keep the angle on the fingers by using the table as a parallel guide. worked really well.
End product. I only removed about 1.5 mm of material, and then cleaned up the shoulder. Can't speak highly enough for having good quality files (Nicholson Single Bastard and Swiss) double bastard for fast removal of the material, than single/finish to lean a clean surface, with the half-round Swiss 00 for chamfering and edge-breaking.
I guess the next steps are to button up the trans side. The PO used red RTV as a gasket, but despite the size I think I am going to try and cut a fiber one. Barring success with that, I will use ThreeBond.