If you want to build a new system with a celeron, I would go for a newer motherboard than a BH6. The BH6 is still a good board, but their are newer boards out their that can do the same and more. Like the BF6 or something. The BF6 isn't very expensive(one of the attractions to the BH6) and it has the nice set of six PCI slots.
If you still want to overclock the AMD with a new motherboard, I would get a Gigabit Ga5ax or a Shuttle. Their is one shuttle that was very good with K6-II and III chips, but I can't remember the model number at the moment. Any one else here know which board I am thinking of? I know the Ga5ax is a good one. I have built a few systems with them this year, and had no problems with overclocking. I made a few K6-II 350's at 400 a while back with the Gigabit. That is pritty much par for a K6-II overclock. Still, I remember seing the Shuttle board as being one of the best, I just can't remember its name.