We can go around all day about how it isn't feasible, but the bottom line is OFFICIALLY.....Both Thor AND Iron Man are 6'6. They both should be drawn as the same height. This isn't like a debate about whether or not Iron Man is as strong as Thor. Even that shouldn't be a matter of opinion but that's a more plausible argument than "I don't think IM is as tall as Thor in armor". That CANNOT be a matter of opinion. How tall are YOU? I'm 6'2. This is not my "opinion" The scale doesn't lie. This is a fact. Some things people simply aren't up for debate.
Also, even if you feel IM should be shorter than Thor, do you really think he should be as short as Romita draws him? This is the reason I started this thread.
For a long time Iron Man didn't even seem like a tech hero. He was just a red and gold superhuman. As result, he never even looked like he was wearing armor but rather just had gold paint on his arms. I don't like this look at all, but I can see how THAT Iron Man might have been shorter. However, modern armors look more like machines, so I agree that it's odd to draw him small. Unless there is a 12-year-old kid in there he should look pretty big. It's a battle suit, not a leotard.
On the other hand, I don't want to see him tower over everyone by a large margin. I wouldn't make him any taller than Thor and probably no broader.