Originally Posted by George1861
The crank & rods are the only difference between the M & the 400. Except for some built in '73, the M/400 have the 429/460 bell pattern.
The rods are the same between the 351m and the 400 ,the Pistons and crank are the difference.
Also the motor was built as the 400 but the stroke ,was changed to the 351,hence 351 Modified, from a 400, because the demand for the 351 cube engine was higher because of the dropped 351 cleveland motor.the Windsor plant couldn't keep up .The 351m crank is a 351windsor crank with different snout.