The GP16 locomotive is unique to the Seaboard Coast Line RR and its successors (Seaboard System and CSX), as the SCL recycled most of its remaining GP7, 9 and 18 units into GP16 units. SCL hyped the GP16 units as speedsters, and assigned them to a new expedited perishable train service (the "Orange Blossom Special") that SCL had just instituted, and hired Johnny Cash to do some PR spots and photos for the new service.
The GP16 units were built, for the most part, by SCL shop forces, with a few x-Clinchfield units being rebuilt by ICG's Paducah Shops. They are the GP16 units with the "yoke" type air filters. On the SCL, the GP16 units were final assembled at SCL's Tampa (FL) Shops (the former ACL's Uceta Shops), with major parts coming from other SCL shops, most notably the former ACL shops at Waycross, GA.
After using them for a rather short time, CSX decided to retire all of the remaining GP16 units. Because most were still in good running condition, and with some good years left in them, CSX had no problem selling them off to shortline operators (like RJ Corman) and the U.S. Army. Consequently, a lot of former CSX GP16 units are still in operation today, but not on CSX.
To my knowledge, no GP16 units were ever transferred or sold to Conrail, or any other major railroad.
ACLfan