Page 40 of the Dolzall brothers book "Diesels from Eddystone" describes the DR-4-4-750 as a "Horsepower boost for a lagging seller." Baldwin dropped the DR-4-4-660 model and introduced the new 750 HP DR-4-4-750. The Atchison, Topeka & Santa Fe (AT&SF) purchased nine in August 1948 and 21 units were sold in 1949 to six different customers.
References
Kirkland, John F. (November 1994). The Diesel Builders volume 3: Baldwin Locomotive Works. Pasadena, California: Interurban Press. ISBN0-916374-93-9.
Dolzall, Gary W. and Stephen F. (1984). Diesels From Eddystone: Baldwin Diesel Locomotives. Milwaukee,Wisconsin: Kalmbach Books. ISBN0-89024-052-3.