If this video does not make you measurably happier than before you clicked "play," your heart is a cold, dead wasteland. Update: some commenters believe that the heavy-set fellow in the dashing sweater vest around 1:08 is Fred "Rerun" Berry, who did indeed dance on Soul Train around this time.
Soul Train Line Dance to The O'Jays "Love Train". Episode #047, 1973.
(thanks, Clayton Cubitt, and more such links here)