I doubt most dealers would even know. You'd have to found one that was around back in the early to mid 90's with a wealth of knowledge.... that they could even still recall. A majority of the dealers that I know are useless when it comes to information, and they're not even close to reliable, half the time they know their sh!t, the other half they're making sh!t up, and taking a stab in the dark as to why things are, the way they are. If you're really curious, Paul at Langs might know, he'll tell you straight up one way or the other, and not guess. He's about the only straight shooter I know in the game.
I personally believe it to be a rigidity issue more than anything, as well as mountability of the push assembly to connect the appropriate A Frames to the headgear. If I were to talk out of my arse, I would say it was because the V Blade was an afterthought to the MM series, and they had to re engineer the headgear to be strong enough to withstand the v blade & the needed A frame structure.
The A frame is a 100% non negotiable item imo, you'd never be able to modify it to work with a MM V blade without hacking, and adding to it, to a point that it'd be considered reconstruction or fabrication. The Headgear...maybe, the spread is off, mounting holes are off...but again, what's the point of any of it unless you're a fabricator, with a bunch of time on your hands, and material to waste.
On another note, for your efforts of frankensteining your pieces together to useable plows....