And if I recall correctly, he was a modern-day man, who was exploited by S.H.I.E.L.D to take a Super-soldier Serum that wasn't complete, and which ultimately killed him.
It was during Ultimates 2.
I think the Cap of 60's-70's will probably be... NUKE!!!
Originally introduced by Frank Miller as the total warped mirror-image of Captain America, a failed late 70's experiment using cybernetics instead of drugs, to create a new Cap.
He makes John Walker look like a picnique... Could be that this Viet-Cap is actually named... G.I JOE!!!
YO JOE!!
Why? Well, it would be neat, because in the Heroes Reborn version of Cap, he was temporarily reactivated during the Viet-war, and apparently started a new legend, about "G.I Joe"...
I suppose it's supremely unlikely... but it would be kinda' cool, now wouldn't it?