Hi, Jerry
The crossover you refer to was the old service lead that passed in front of the sand house and the former coal tower. Today, the noise of the wheels on that crossover would raise the hackles of neighbors more than the smoke.
I'll go back and see if I can narrow this down closer from photos, but it seems to me that it was still there in '71 and gone by '74. Even as late as '76, the real estate where the old yard had been was still in place awaiting the new highway relocation, which obliterated the area from what it had been previously.
As you probably know, many people are under the impression that the D&RGW did the new loop for the sake of efficiency and/or lack of any interest in historical preservation, but it was actually done because the State Highway Department condemned the old yard and the old lower loop well before construction was begun.
Actually, now that I think about it, the first part of the highway project probably affected the old loop first, which caused the new loop to be done when it was.
If I can find anything useful to answer your question, I'll post it in the next day or so. But I think it was still there in '71.