Hy LAJones48, you are correct, the factory block mounts have only two round bolt holes to bolt the mount to the engine block. The only reason I can think of for the "extra" holes is to possibly allow the mount to twist to clear some of the larger harmonic balancers available on some of the higher horsepower small block Chevys, the mount "stilts" are long enough that the "misalignment" may still be within range, hope that helps.
