Okay, so, that bike of yours is really confusing me. I keep looking at it and trying to decide what all is going on there. I have 4-5 Monark badged Huffy-built car bikes and none of them have any "M" bolts anywhere. You have a Bendix 76 hub on the back wheel but your serial number says it's a 1965. So I don't think your wheel set is original to that bike. Also, I have one Huffy with that type of rack that is badged as a Firestone bike but that's the only one and I've always wondered about that bike and that rack. It's not a Huffy-made rack or it's one they used very, very briefly. It looks more like a Murray rack although I'm not saying Huffy didn't use it. And the chain ring is not correct, as stated above. I keep staring at that tank as well. The graphics on the top of the tank are what my Monark bikes have but the font used on "Corvair" is the type of font they used earlier on bikes like the Belair, Thunderbird, etc. I don't remember seeing that type of font on any bikes in the mid-60's. Finally, I can't tell if you should have had a bezel on there because the screws for one are there but then that crown right where the bezel would be makes no sense. Huffy always put that logo up above the bezel whether it was "Monark" or "Huffy".
My best guess is that Huffy threw together some parts they had around to fulfill a Monark contract. They did that with Firestone badged bikes sometimes too. I've seen them also do that with lots of girls bikes all the way into the 1970's. That may be the reason you have a Bendix 76 wheel set on there. Or someone may have pieced that bike together after the Bendix 76 wheel sets came out.
All in all, that bike is a confusing affair!!! Very cool, just confusing.