Airborne Express is an express courrier with no passenger ops as far as I know. They use specific ULDs that can be loaded through the normal passenger front door, that's the reason why there is no cargo door on the main deck. The 767s are early -281s series bought from ANA.
There are special containers for the 767, since the door is bigger. But, the containers from the DC-8/9 will fit into the 767 and they ARE used. There is no cargo door. The upper deck is used for these ULDs and the cargo bay holds more of these containers I believe.
Airborne Express is based out of Seattle, but its hub is located in Wilmington, OH. Wilmington is about halfway between Cincinnati and Columbus. The airport that Airborne is based from used to be Clinton County AFB. But in 1977, the USAF abandoned it, and Airborne moved in.
It also looks like Airborne has put a few of TWA's old -231s in service as well, 4 of them. The remaining 5 are stored, and may be on their way as well. Rumors were a few weeks back that Ansetts 762s were going to Airborne as well.
The article in Airways was quite good indeed, including a section on how Airborne Express converts the aircraft from pax to cargo. The 747 also has windows on its lower deck in older models, and the upper deck (even on the 744F) has windows for the crew.