The fastest K6 I've heard of is the 550MHz K6-2. I think there may have been a 600MHz model, but I'm not positive.
You might be able to push your 450MHz to 550MHz...but realistically you probably won't be able to go that far with it...maybe 475MHz or 500MHz if you're lucky.
The K6 wasn't a very good overclocker.
If you do play around with it, make sure you get a better heatsink for it...or at least remove the heatspreader cap from the chip.
Honestly, I wouldn't bother.

Cricket