Well, I'm updating an older thread. I found a deal for a Pal8045 with a Papst fan on eBay that saved me about $25 rather than buying it new, so I jumped on it and decided to try installing it on my ECS K7S5A rev. 3.1 even though JackBurton didn't have any luck. I figured I could always sell the heatsink/fan for about what I paid for it anyway.
Long story short, it fits my motherboard. The noise from my case has been reduced immensely and I can't wait to make 1 or 2 more modifications to further reduce the noise on my system (lord knows I wish I'd bought Seagate Baraccuda IV drives). I'm cooling an Athlon XP 1700+ and have been running Seti for about 4 hours so far with no problems.
However, using SpeedFan, it seems that my CPU temps with a full load are 68 degrees celcius, which I understand are quite high. I didn't use any artic silver, so that might be an option to reduce the temps somewhat, but I don't like the idea of having to uninstall and reinstall the heatsink again. It's quite a bitch to get onto the motherboard. So I might just live with high temps, as long as they don't effect the overall system stability. Knock on wood. Anyway, just thought I'd let you all know.