In 1966 The Amazing Spider-Man was still drawn by Steve Ditko, who will quit with #38. This is the cover Ditko prepared for #35, as published in Italy in L'Uomo Ragno #29.
However, this is not the cover published in USA. Someone at Marvel did not like the -let's say "peculiar"- pose of spidey, and asked Jack Kirby to correct it. The final cover, as published in AMS #35 is this
If you look closely you will notice that Kirby also modified Molten's costume. Maybe the one drawn by Ditko was too small ;)
Here is the detail of the costume, in red Kirby's retouched version