DC-8 launch dates and range

I was doing some reading into the DC-8 recently, and I noticed some discrepancies between some of the Super 60s launch dates. The -61 is currently listed as launching in 1962 in the database, but the program wasn't announced until 1965. According to the airliners.net page on the DC-8-60 series, and the Flight International archives, the -61 and -62 started delivery in 1967, followed by the -63 in 1968.
 
As far as their range goes, I also looked at Boeing's Airport Compatibility documents on the DC-8, and in the performance charts, it seems that according to the manufacturer (or at least the manufacturer's successor), the ranges at MTOW differ somewhat from what AE has now (Notes: The charts require some interpolation, and the -50 as shown in the charts is the -55, the model with the highest MTOW).

In summary: the -50 has too much range, and the -60s series aircraft have too little range, with the -62 actually having more range than the -50.
 
A comparison:
-50: AE: 5653 nm / Actual MTOW range: ~3900 nm / 189 pax and baggage: ~4600 nm / a.net: 4970 nm
-61: AE: 2763 nm / Actual MTOW range: ~2500 nm / 259 pax and baggage: ~3200 nm / a.net: 3256 nm
-62: AE: 3754 nm / Actual MTOW range: ~4500 nm / 189 pax and baggage: ~5200 nm / a.net: 5210 nm
-63: AE: 3647 nm / Actual MTOW range: ~3300 nm / 259 pax and baggage: ~4000 nm / a.net: 3907 nm
 
Sources:
DC-8-50 airliners.net page
DC-8-60 Series airliner.net page
DC-8 Boeing ACAPS PDF, Aircraft Performance section starts on page 45