You say Cleveland (Windsor) like they are the "same thing"... and you "know what you're talking about". THEY'RE DIFFERENT BLOCKS. They have different deck heights, width, etc. The M-code also does not have "larger pistons", it has higher compression heads. Aside from the C and W having
different deck heights and block widths, many other parts don't interchange at all. '71s were also available with
three versions of the Cleveland, and two big blocks, so any argument about semantics when it comes to GT7s version really doesn't mean anything.
Is this what you do, run around the forums pretending to know things when you're talking out of your ass? I know because I've been working on Fords since around age 5, have a storied family history of BOSS 302 and 429 Mustangs, racing 289 and FE Galaxies and Falcons, pretty much anything Ford from 1940-present day, have a passion for cars in general and research things I'm not 100% sure of before trying to educate anyone about them... so I "know what I'm talking about". But just in case, here's an article on C W and M engines.
Hagerty - Mustang Clevelands and other engines