First of all, Welcome to the forums.
That being said, let's get to the challenge.
Unlike the K6III's, the K6-2's are not known to overclock very well. Although I have no experience with that particular motherboard, I've been successful with the K6 line of CPUs in the past. I've had a K6III+450 up to 616MHz until I let the smoke out of it, and still have a K6III 350 out there running at 450MHz. There may be some hope for you.
Keep in mind that there are no guarantees, there is always a certain amount of risk involved, especially when compared to the later offerings from both Intel and AMD. Also don't expect PIII or T-BIRD performance from that aging platform.
Now down to business. After a quick look at the link for your motherboard, I can see that it will support several different FSB settings, 66 through 100MHz. These settings would be located at "SW3 (B3 & B4)". From what I can surmise, these would be DIP switches.
According to the chart there are multiplier choices ranging from 2.5X through 5.5X. These would be set at "SW2 (B1, B2 & B3)".
Voltage can be set by "SW2 (B4 through B8)". This may be a problem depending on what the default voltage of you CPU is, I'm guessing that your default is 2.4V, which isn't available on that board. The next setting is 2.8V. At that setting, I think you're beginning to push the limit. Watch your cooling!
This brings up another issue, heat. A motherboard that old probably doesn't have any method to monitor the temperatures, you have to take it a little at a time. When you get to a point where you have the heat related symptoms, lock ups, blue screens unexplained errors etc, it's time to revisit your cooling. The factory hsf is not going to be enough to keep the temperatures manageable once you start to increase the voltage. I would suggest that you upgrade to a socket A hsf from the later DURON/T-BIRD CPU's. I've had good results with the Global Win FOP32, it's worth a look if you have the room around the socket for clearance.
As mentioned above, look for a more current BIOS, this can cure a lot of problems.
I think that you can reasonably expect 400MHz with relative ease, make sure that you look at the cooling. If you continue to have problems attaining a higher clock speed, try lowering the FSB speed a bit, a 95MHz FSB at 4X will yield a clock speed of 380MHz, and you may find that you're able to hit 4.5*95 (428MHz).
And lastly, keep an eye on how much money you invest into this endeavor. No matter how fast you get the processor to go, you're still going to be saddled by the slower memory, hard drives and other peripherals on that aging socket 7 platform. A new socket A motherboard along with a DURON processor can be had for not much more than a few upgrades to an old system. Even a low end DURON system will give you blistering performance compared to whatever you can get out of your current system. Building an inexpensive system based on the newer socket A platform will also give you a viable upgrade path to well over 1G.
Good Luck!
