You should be fine if you have a decent aftermarket heatsink/fan and good case cooling. I'm running my K6-2+ 500 at 5.5x100 at 2.2 Vcore with a FEP-32 and it runs at 54C rock solid after cracking RC5 all night in my hotter than h*ll dorm room (and I'm not kidding, its super hot in this room).
You've checked to make sure that the chip will run in that mobo, right?
Also, you can check out
this board
They seem to be a bunch of die hard K6 fanatics (sorta like me

) and might be able to lend some advice.
Good luck!
Chuck