Oddly enough I came across this PDF from Boeing.  it has some info on a variety of DC-8 models, including takeoff runway length vs. weight/altitude for the DC-8-55, and DC-8-55F info too:

 

https://www.boeing.com/resources/boeingdotcom/commercial/airports/acaps/dc8.pdf

Boeing bought McDonnell Douglas in 1996, so all the Douglas documentation now lives at Boeing. 

 

This also explains how the MD-95 turned into the Boeing 717. 

 

EDIT: Though this is a 1989 document that refers readers to McDonnell Douglas for more information. So that really is odd. I wonder what the background was.