What with all the issues of putting an LC575 board in a stock CC, at its default resolution (and no physical mods), and that obscure errors like these will occur without any ResEdit patching ...

I'd just pull the SCSI HD, install an universal system onto it from another Mac, apply your ResEdit patch on that Mac, and plug it back in your CC. Alternately, do you have the original CC board to put back in for a little while?

JB