YOu can run that processor on most boards that supply dual voltage. Even the earlier Pentium MMX boards that ran at 2.8v core will usually work. You can run it at 6x66.6 if needed using the 2x multiplier, which is converted by the CPU to 6x. And the core voltage of 2.2v, well, 2.8v is tolerated with a larger cooler, I recommend a cheap Athlon cooler.
The reason I mention compatability with older non-compliant boards is because of the price difference-the older boards cost aroun $15-20, while the newer proper boards cost around $50-60.
x2 as x6 multiplier only works in k6-2 400 with stepping 8 or higher (just check www.amd.com) and ALL k6-3. So, your k6-2 350Mhz don't have it. Also, older non super7 motherboards can hold it. I have an Asus SP97-V with an unsupported 83Mhz than run smoothly, an even the official manual don't say anything about k6-2. So, surf the net and find others. In my case it have a k6-2 500 and I use the x6 trick (83x6) to reach 500Mhz :-)
As people say, check dual volt and compatibility issues before you buy any MB.