I fail to see the point in retro overclocking. I overclocked them back in the day ... 12 years ago, but there was serious money to be saved by overclocking a 1.8A instead of buying a 2.6GHz. P4 gear is recycling material as it has virtually no monetary value. It's not like you can learn much from overclocking a P4 anyway, the modern chips/boards are way different.
If you want to buy gear then get the requisite number of posts and ask in the members market.