That much is obvious from your choice of candidate.
What's wrong with McDonnell? He sounds to me like true Labour, not New Labour. (Not that I'd support him over your average Lib Dem, of course.)
McDonnell isn't any "truer" to what the Labour Party was in 1900, 1918 or 1945 (or any other significant date in party history) than the current incumbent of the leadership position. He's New Left, basically, and rose to prominance on the GLC.
True, would you say anyone really counts as an "Old Left" candidate, maaybe meacher, and I wouldn't say he's "very" left-wing.. What would that make McDonnell?