A '66 B body might be a 318 Poly, and I'm not sure about the pulley spacing. Likely no, as Jake said.
However, Poly 318's are very similar on the bottom end to later LA's. It would depend on the head bolt boss location on the ends, like for the alternator bracket and such. You would need a tape measure and a small machinists square, and measure between the two. Intake bolt pattern is different, so anything there likely won't work.
