I have never read the Giant-Size Marvel Super Heroes with Spidey and Morbius, so wouldn't know where it shoud fit. I see it has a publication date of June 1974, so what would it be doing in a 1972 and 1973 stories volume? It makes no sense. This would belong to an hypothetical MTU Masterwork to me.
If 121 and 122 are pushed to #13, THAT volume is going to be heavy-duty, what with the death of Gwen, the death of the Goblin, the first Punisher and the first - *gasp*, *shudder* Spider-Mobile...