Start out with quality components and you will be ok. Achieving 150 MHz bus speed isn't just a matter of going into the BIOS and selecting it.
Most importantly you need top quality RAM (Crucial CAS2 PC133, Mushkin Mosel Vitelic rev. 2, EMS HSDRAM, etc.)
Then you'll need a mobo known to run at that speed, you'll need a vid card that can handle the AGP overclock (different video chips interact better or worse with different motherboard chipsets), and last but not least you need a CPU that's going to actually make the target speed. That's probably the trickiest part right there. You can buy everything else having a good idea of what it'll achieve for you, but the CPU is more of a crapshoot.
Right now, to be safe, stick with a retail PIII with cB0 stepping rated at 650 MHz or less to have the best chance of getting it to run on a 150 MHz bus. That won't get you over a GHz, but the extra system bandwidth you get running a 150 bus more than makes up for not having a whiz-bang 4 digit CPU speed.
Good luck, hope you get there. Let us know if/when you need help.
-Pain