Here's the original art for Marvel Treasury Edition #13, also known as the "Giant Superhero Holiday Grab-Bag."
Here's the final so you can play count-the-differences...
Bear in mind, too, that all that was must have been done using photostats and paste-ups. The production crew likely took a stat (kind of like a super-high-quality photocopy) of the original art and manually cut out Daredevil using an Exacto knife. Then cut out and re-positioned Thing's hand. Then cut out and repositioned Iron Man, followed by re-drawing his right hand, half of which wasn't originally visible. Then cut out and re-drew Thor's cape. All of this cutting would have had to follow the inked lines precisely, so they could slide the logo underneath all of it and make sure there weren't large gaps between the figures and the letters.
I can almost guarantee you that the production folks on this cover were doing more than a little cursing at all the changes that had to be made after Sinnott turned in his inks! Yuletide greetings, indeed!