The Mighty Mego Thor was among the first heroes to be issued solely
on Type II bodies in 1976. He, Conan and
the Fantastic Four share the distinction
of never having been sold on the type one body.
Mego Thor greatly benefited from being a later Mego release. The
Vac-metallized helmet is attached to a small hole in his head
with a post inside the helmet, this often found broken on loose
figures. His very cool boots are yellow rubber. His hammer Mjolnir
is an often missing accessory.
Thor is also known to come with a vinyl cape, this was a short run variant for Mego figures. Other known vinyl-caped figures include Shazam and Batman.
Here is a side by side example of the variations in Thor's armbands.
Accessory
Check: Click here to identify original
and repro parts. 
Boxed Mego Thor in it's Kirby-esque glory as you can see Mego did some running changes. (courtesy of Tom)
Another view of the box courtesy Scott Adams.
Carded 1975 Mego Thor which is more commonly found than other cards, courtesy of Dan Crandall. There is no 1978 Thor card.
1979 Carded Mego Thor is the toughest to find packaging variant for this character (note how the locks are subtly different),