A few more details from from a later edition of Flight (5 Feb 1960, pg 187)
http://www.flightglobal.com/pdfarchive/view/1960/1960%20-%200187.html
This Boeing 707 development was offered to meet an American Airlines specifications for an all-cargo aircraft (either an intermediate range 40-60,000 lb payload or a long range 80-100,000 lb payload turboprop or jet aircraft).
[An all-cargo version of the DC-8 (no details) was also offered. Lockheed's GL-207 Super Hercules and the swing-tail Canadair CL-44D had both failed to meet the spec but revised versions of both type were, at the time of writing, expected to be submitted.]
The all-cargo version of the Boeing 707 was the Model 735-28 which weighed 315,000 lb, had a payload of 93,766 lb, and would cost $6,825,000 in 1960 US dollars. A Model 735-30 was also on offer "with higher weight and increased thrust priced at about $8,025,000. In addition to American Airlines, Slick Airways is also reported to be interested in the Boeing 735."