Greg,
Not quite sure what engine you saw, but if the 1981-1985 timeframe is correct, the only engine that it could have been (in Central City anyway) would be Colorado & Southern 2-8-0 #71. Both of the IRCA (El Salvador) locos were already at the Loop. #44 arrived in Silver Plume in 1973, and #40 arrived on the scene in 1978.
If you were in Central City before or during 1978, the engine could have been the #40.
If anyone else can help in more detail, please chime in.
Don't know if this helps much.
Shane