I was in a salvage (oops, to be politically correct, recycling) yard yesterday. I saw an old (mid-late 70's) Ford LTD in there. The side of the valve covers, if I remember right, said something like "cubic inchs: 351 engine family 351M/400". It may have been a little different in the wording. But I'm sure it was 351 c.i., and somewhere it said 351M/400 on it. What motor is this? I know of the 351W and 351C, but....
Steve