Pretty good info. If it came from memeory then you are a true fanatic.
Just some small corrections and additions
The 70 series does not have APU's installed. The only DC8's I know of with APU's were the 2 62 series planes owned by MGM Grand which were converted to freighters about 4 years ago. MGM had the APU's installed.
There are at least 2 and if I'm not mistaken a 3rd.
One is owned by NASA Langley research, and the other is a corporate jet. I believe another exists also in the corporate guise.
The 50 series including the 55 had a range of JT3 engines. The 55/61 had JT3D-3B powerplants, and the 62/63 had the long duct JT3D-7. The -7 incorporated a hydraulic reverser system in contrast to the pneumatic reversers on the 50/61.
The range improvements on the 62/63 series came primarilly from new engine nacelles, new engine struts, and a new wing.
The DC8 70 series is still one of the longest range airplanes flying in the saame category as the 777, 747, and the A340.
Cammacorp designed the 70 series modification, and performed some of the modifications. But many airlines such as delta did these mods themselves.
More than half of the DC8's built are still flying. The airframe has no design life. It was overbuilt. It's life expectancy is expected to be about 120,000 hours. A majority of the airframes flying today are in the 50-75,000 hour range.
The DC8's converted to 70's in the early 80's were all reduced to zero time airframes. So they will be with us for at least another decade, or until spares run out.
The planes destined for UPS have a revised foward panel incorporating an EFIS PFD (Primary Flight Display).
I have flown both the 55/61 series, and the 62.63 series. I enjoyed the 62 the best. More powerful engines on a lighter airframe.