This post reminds me of the first two B1 motors I knew of, Bob Mazolini had both. The first one was a 417C.I. motor bought from Koffels to use in a Super Stock modified 1964 Plymouth Savoy raced in SS. I don't know the bore and stroke but it was in a KB aluminum block so I',m going to assume a short stroke with a large,4.500?, or so bore. Bob had to learn where to shift it which meant at 8600 RPM, not 8650 or below 8400 RPM to make it run fast. It had a set of Dominator carbs on a tunnel ram. His second motor was smaller and had the laterB1-MC heads on it, it had coolant circulation problems at the rear of one side of the block, it would kill the exhaust valve spring after one run, he blame poor machining or casting on that block for the coolant not circulating around that valve spring seat area.
I don't remember him saying how much power those motors made back then in the 1980 and 1990s, the first one ran way under the index, not sure about the second one