Difference in doors?

[dooce]

I've noticed that there are two different parts numbers for a new door depending if you have 73-76 or 77 and later. I've also noticed comments on people mentioning differences but never putting it in detail. Are the two doors interchangeable? I have taken a look at a set of 76 doors, and a set of my 86 doors and cannot find an obvious difference. Am I just not paying enough attention? I didn't think they would reproduce a different door for something so small, just like they don't produce a 79-80 specific hood (or not that i've seen). Please someone shine the light. Thanks DOOCE