Not only does Thor appear on this backgroundless Gil Kane/Frank Giacoia reaction shot cover, he also shows up in some Sal Buscema/Joe Staton panels inside.
This issue features the first parts of two origin stories, one of which Thor witnesses.
Thor was not on the Gil Kane cover of AVENGERS #97. He did appear on 6 of the 21 interior pages. Thor's 24th 1971 appearance, his 185th of all time.
The newest issue of THOR featured the mind-boggling Mangog. John Romita becomes the second artist to do a Mangog cover. Kirby, of course, crafted the first 3 Mangog covers.

IMMORTAL THOR #5 $4.99