DC-8s were originally outfitted with a pair of speedbrakes on the belly, just aft of the wing trailing edge. They were ineffective, so the aircraft ended up getting certified with #2 and 3 reversers that were operable at flight-idle.
That applies to the -10, 20, 30, 40, 50, and Super 60s. The Super 70s with CFM56s, I'm honestly not sure about.