Well....watch these... 
  
DC-8-40 serie RR Conway engines 
  
http://www.airliners.net/photo/Alitalia/Do...next_id=1185613 
  
DC-8-50 serie P&W JT3D-3 engines 
  
http://www.airliners.net/photo/Cyprus-Airw...next_id=1460172 
  
DC-8-61 serie P&W JT3D-3 engines, streched fuselage 
  
http://www.airliners.net/photo/Capitol-Air...next_id=1455866 
  
DC-8-62 serie P&W JT3D-7 engines 
  
http://www.airliners.net/photo/Alitalia/Do...next_id=1080830 
  
DC-8-63 serie P&W JT3D-7 engines, streched fuselage 
  
http://www.airliners.net/photo/Air-Transpo...next_id=1458598 
  
And the 70 series is the reengined version of the 60 series with the CFM-56. 
  
http://www.airliners.net/photo/United-Airl...next_id=1460171 
  
Plus.... the pylons are wrong (taken from 707), spoilers, tail and giant main undercarriage.