https://www2.irm.org/blogs/archives/216 ... -SD20.html
"The SD20 remanufacturing program sourced SD7, SD24, SD24B and SD35 locomotives. 42 of them were completed between 1979 and 1982. ICG 2002 was the third SD20, released on October 24th, 1979, and was originally a Union Pacific SD24B, numbered 427B. Some of the features on the SD20 included upgraded 16-567CE roots blown engines, clean air inertial blower cabinets, and cabs similar to EMD’s second generation spartan cab design....ICG 2002 was built as UP 427B, a SD24B (cabless booster)"
This likely will be the only example saved. I have heard that they were very slow, the joke being that if you threw one off of a building it would take a few minutes to hit the ground. Top photo (credited to Darrell Land on RRPA), 1980; bottom photo Steve Forrest, 1979.