I'd suggest not going all the way to 1 GHz right off the bat. If you fry your processor, that will be the end of it. Maybe you should aim for something like 700 or 800 MHz, and then gradually step it up to make sure no issues arise. As far as cooling, an LCD replacement for the CRT will not only open it up, but speed up heat dissipation, so that is a definite start. With that extra space, you might be able to put a better heatsink over the processor, and perhaps add a fan. You might also consider putting a fan at the vent on the top drawing fresh air in. That will expedite the cooling process, and is how the G5 case cooling system works.
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Cheers! :-)
- JediJoker

Current:
- "ProBook:" 15.4" MacBook Pro Core 2 Duo 2.33 GHz
- Mac Classic II
- Old PowerBook

Moved On:
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- Purple iMac