This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
It is not hard to do at all... I mounted the motherboard with the expansion cards going horizontal in relation to the ground (you need to drill some extra holes in the tower case because the GS has different mounting holes than the PC). The cards are light enough that they stay put this way. The only time this could be a problem is with unusually heavy cards, like the Focus or MicroDrive units... The cards don't line up with the openings on the case, but that's not a problem because Apple cards, unlike PC cards, have ribbon cable extended DB connectors that can be mounted on the openings at the back of the case... For the power supply, I rewired a PC power supply to feed the GS. The voltages are the same, so simply match +5V with +5V, +12V with +12V, -5V with - 5V, -12V with -12V, and the grounds and your GS will be ready to run! The PC power supply (250 watts) and fans have a benefit...my GS is more stable now than it was in its native case. I recommend this upgrade for those who feel up to it. Use a full tower case for the best results and most room to work with. By: Supertimer