Shapeshifter works with 8.1 on a CS II 68060.
You need to install 8.0 "for any mac" first. Also there was a "setfpuexceptions off" command that i had to have in my startup-sequence.
8.1 does work but it is significantly slower than 8.0, which is much slower than 7.6 and slower still than 7.5.5. There is a 7.5.5 out there skinned to look like 8. I used that. It flies on a 68060, and really you're not missing much functionality: I think most stuff that ran on 68k 8 ran on 68k 7.5.5.