Hey Nick! Hope you're going well in your neck of the woods.

I quite like the LC580 too and I'd definately go the 40Mhz overclock, and a full '040 too. Shove in a more modern hard disk (eg. a 20GB), but I wouldn't bother with the CD-ROM as the 24X isn't much faster than the 8X - not due to onboard SCSI speeds, it's more due to little difference in speed between the drives themselves.

Currently nearing the bin is a 5500/250 board, it's physically compatible in the 580 but not sure if it'll work, happy to post it your way if so.

Cheers

Jordi