I've been nursing this z60t with GPU/systemboard issues for a few years, and I think its finally reached the point of no return as the last linux Distro known to not freeze on her is now freezing.

So.... time to rebuild her. What can I replace her MOBO with, if I can scrape a good one off fleabay? Pref upgrade rather then downgrade.

Your Z60t is nothing more than slightly souped-up T43, but without the T43's original SATA-PATA bridge.
It's not the software that's failing, but the hardware.
It's most likely a failing Southbridge (big Intel chip under the wifi-card).
Open her up, remove the wifi-card, put pressure on it (try different corners), and try to boot.
If it now works, you have the culprit.

If that's the case you are in luck.
Contact forum member poshgeordie in Newcastle for a chip reballing.