Time for another look at original Marvel covers and the covers those stories were reprinted in!
First up, Fantastic Four #100 and the reprint in Marvel's Greatest Comics #81... and I have to admit, at first glance, all I really noticed was that the cover was shifted down... until I looked closer, and realized that there were other changes! Most obvious is that the Torch figure is completely different between the two! Also, the Sandman figure is new. I think Namor was redrawn, too. The Super Ape has been altered, mostly his right han. I believe the Mad Thinker has been redone, too... and then there's a mystery... look next to the Dragon Man's head on the reprint... who is that supposed to be in the blue mask and red tunic? My best guess is that it's supposed to be the Trapster, who's been covered up by the UPC code on the reprint (although he is still there).
Next, Amazing Spider-Man #74 and the reprint in Marvel Tales #55... and it looks like mostly a recoloring job, with the art reduced somewhat and some new art added on the right (note the different details on the side of the tablet). I'm not sure why the stripes on the one goon disappeared on the reprint!
Next, it's Thor #127 and the reprint in Special Marvel Edition #4... and it looks like the alterations were just done to accommodate the cover dress of the time.
Up next, it's Amazing Spider-Man #76 and the reprint in Marvel Tales #57... and there was a mess of changes done! Figures were cut and pasted around (Spidey and the Lizard are rotated against the background). This must've been done to accommodate the logo.
Now we're up to Fantastic Four #20 and the reprint in Marvel Collectors' Item Classics #14... and there are changes dne here! The most obvious one is that the Torch has made more of a clean hole in the concrete, but you may have noticed that the building in the background is pretty much gone, too! The Molecule Man's energy beams are different, too.
Next, Avengers #14 and the reprint in Marvel Triple Action #8... obviously an all new cover, but the original was so much better, don't you think?
Next, it's Hulk #131 and the reprint in Marvel Super-Heroes #83, and other than some recoloring, I don't see any changes.
Finally, it's Avengers #62 and the reprint in Marvel Super Action #23, and there's some minor changes done.... the whole image is shifted down, some of the background has been altered (filled in blacks), and I think the smoke with the floating heads has been moved a bit, too.