Not really, there's a lot of overlap between the far left and certain libertarians.
Except McGovern isn't that far left. He's a fairly standard liberal, at least on economic issues. There may be some overlap on social issues, but I'd still say there's a good amount of distance between the two.
McGovern was a mixed bag economically - his proposal for a minimum guaranteed income was fairly ludicrous, but he also campaigned for a balanced budget. Socially, there is little to no distinction between McGovern's platform of 1972 and my own political views, though I'm certainly somewhat to his left in general principle.
Anybody who would have voted Nixon in 1972 and claims to be a libertarian is a scum and an unprincipled hypocrite.