I have a 1GHz "B" Tbird (100FSB). I run it on an Abit KT7R mobo, w/a FOP32-1 HSF. I cannot get the multiplier above 10.5, stable even with the FSB running at only 100MHz. It'll do 11x, but not stable. 3DMark will lock up, etc.
My FSB I've gotten to 107, but not stable. I think that's more a shortcoming of my Infineon ram though. Currently, I run 10.5 x 105 @ 1.800 volts. Stable as a rock.
I wouldn't get a 1GHz "B" CPU. Higher rated chips can be had for very little additional cost and have been known to overclock better. With prices on "C" Athlons dropping every day, If I was starting over/fresh, I'd just get a 1.4 and not OC at all. MHO.