The 70/71 B20E had the hisghest original HP rating, at 130 HP. But if you are rebuilding an engine it doesn't make much difference which one you start with, although I hear the B20F (112 hp as new) head makes a better start for a modified head.

150 - 160 HP is somewhat easy to obtain out of a tweaked B20 (cam, head work, exhaust). And the cost rapidly rises as does the HP - with the most probably being 250 HP or so out of a specially built engine with a supercharger.

PV's sound slow now, but they were the BMW of their era. Originally they were stuck with lower output versions of the B18 engine - probably in an attempt to make them slower than the 2 or 3 times more expensive P1800 sports car. They were designed before the obsessive safety design ethic that began with the 122 and P1800, and a PV weighs about 300 - 350 lbs less than either of those cars. So a PV will be a bit quicker with a given amount of HP than would a 122 or 1800.