b210 seats did not fit neatly in my 210 it required doing bad things to make them fit. the seats were out of a 79 and i was putting them in an 81. I think i used the 79 rails and made the bolt holes really large (or something) the end result was seats that fit and had less holes.

IF you have a datsun that didn't come with a catalytic converter these things are not an issue as much, in CA the cats keep getting bigger and the mountings for seats gets wackier.