If you don't have a lock like on an NForce2 board, you will want to try to keep them as close to stock as possible. Stock PCI is 33mhz, stock AGP is 66mhz. These numbers come by applying a divider to your FSB. The divider for a 166mhz FSB is 1/6, so you get 33mhz for PCI, and AGP is always double of what PCI is.
But you have an NForce2 so I wouldn't worry about it too much.