You know the drill by now, right? Original cover and reprint... let's go!
First up, here's Tales of Suspense #98 and Marvel Double Feature #21... obviously the blurb's entirely different, and the figures have been shifted down... but note also that it's been rotated counter-clockwise, and it looks as though the Black Panther figure's been altered a bit, especially on the head.
Next, we have Avengers #38 and Marvel Triple Action #30. The while image has been reduced, obviously, but look at Hercules... his head and part of his torso has been redrawn, and the Enchantress and the rock she's standing on are all new as well.
Pretty straightforward here with Daredevil #9 and Marvel Super-Heroes #29... it's all new, and not an improvement! I'd think that the original image could've been cut and pasted for Daredevil's part of the reprint cover.
You don't often see the image flipped for a reprint, but that's exactly what happened when Amazing Spider-Man #114 was reprinted in Marvel Tales #93. Along with that, we have a slight enlargement of the original image, too, in order to accommodate the cover dress. Note also that the balloons have been redone entirely.
When Sgt. Fury #8 was reprinted in Special Marvel Edition #6, an all-new cover was done... but not an improvement over the original!
Finally, we have Silver Surfer #13 and Fantasy Masterpieces #13... this one desn't seem to have been changed, except maybe just being reduced a tiny bit.