A CO DC-10 on DEN-MIA wouldn't surprise me for the late 1970s/early 1980s. CO flew quite a few DC-10s domestically way back when, and had DC-10s on IAH-DEN into the early 1990s.
My one and only DC-10 flight was in September 2001 on IAH-LAX, a week before 9/11, and just under a month before the last few DC-10s were quickly retired from CO's fleet.