The 166 MHz one only works in 166 MHz PowerBooks: "Compatible with PowerBook 1400 166MHz models only". I've also read about this elsewhere. It's different for some reason. I'm also getting the processor mainly for the cache which helps a lot.

I don't think I can repair the old board unless I have a dead logic board that I can steal the little block of battery pins from. Nobody seems to have a dead 1400 logic. It would be too difficult to put a new pin into the block but it might be possible to solder a piece of copper to the underside of the board and maybe bend it up to touch the battery.