That could be it. MacTracker says the LC 475 needs System Enabler 065. I went with 7.5.3 because the enablers are built in to the system folder, if I recall correctly.

I thought I did a universal install, but now I can't be sure. I'll blank the drive on another machine and ensure I do a universal install of 7.5.3. Or maybe 8.1.

Fingers crossed!