[Shaggy]

Duece is right for the most part except not all clevlands are 4 bolt motors. The M motor is a small displacement big block loosley based on the Clevland design and the Clevland is a big displacement Small block (the M has big block motor mounts and bellhousing pattern and the cleavland has small block motor mounts and bell pattern.) The M was a smog laden pig wihtt big main bearings as well bigger than even a windsor motor. Which is the reason you can turn down a 400 m crank to windsor mains and create a 408 stroker with one. The old poor boy combo was to use a 400 crank chrysler rods and 302 pistons to make a 408 i don't remember now which chrysler rods they were other than to say it was one of there six cylinders.