Yep, friends, it's time for a bonus edition of Cover Redux!
This bonus edition starts with Fantastic Four #63 and the reprint in Marvel's Greatest Comics #46. Looks to me like the art was reduced for the reprint, and possibly some extra art added on the left-hand side. Some detail was lost in the statting.
Next, it's FF #23 and the reprint in MGC #25... and I believe the art was statted larger for this reprint, and shifted down. You can see that the statting didn't work well for the Kirby Kollage in the background.
Next, we have Avengers #28 and the reprint in Marvel Triple Action #22... and this is a case of reducing the original art for the reprint, and possibly new art added to the sides, mostly on the right. The rocks next to Quicksilver have been reinked to an extent, too, with more shadows.
And that brings us to Incredible Hulk #141 and the reprint in Marvel Super-Heroes #92. This is another case of sightly reducing the art and shifting it down, this time to accommodate the logo. I also note that the background has been altered behind the logos, so that in the reprint it's all rocks and rubble.