I made a forum post about my $20 Craigslist find that I turned into a pretty cool K6-3+ system:

Turning a $20 Craigslist purchase into a respectable DOS/Win9x gaming rig

I am just posting this following up with additional issues I had and when using TweakBIOS and what I did to solve them

Issue #1: Running a DOS full screen program and then returning to Windows 98 SE would freeze the computer. It did not matter what the FSB speed was.
Resolution: It turns out my Voodoo 3 2000 PCI did not like to have the ROM BIOS Cached at C000-C7FF. I had to change this in the Advanced BIOS setup to Shadow only.

Issue #2: Running higher end 3D game like Quake 3 would just cause the system to reboot. Again the FSB speed did not matter.
Resolution: I used TweakBIOS and had an option under the 430TX CPU-to-PCI Bridge to enable Extended Signaling. That again did not play nice with my Voodoo 3 2000 PCI card. Turning off the setting fixed the issue.

Issue #3: Using TweakBIOS to enable Ultra33 DMA mode would cause issues when running SCANREGW in Windows 98 SE. SCANREGW would complain it had trouble accessing the registry, when in fact it did not. Killing the program with the Task Manager and running it again manually would result in no issue.
Resolution: I think this was a timing issue, because I created a startup batch file with a 30 second delay before running SCANREGW and have not had this error since.

After doing all this, I have had absolutely no further issues with this motherboard. I think I have squeezed just about all the performance I can out of it now. The K6-3+ is running at 500Mhz and I was able to overclock the Voodoo 3 2000 PCI to 166Mhz after installing an aftermarket cooler. I have installed 256MB of PC133 SDRAM. This computer will now give even a Super 7 system with AGP a run for it's money:)