A GP8 is a four-axle diesel locomotive

Diesel locomotive

A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...

 rebuilt by the Illinois Central's

Illinois Central Railroad

The Illinois Central Railroad , sometimes called the Main Line of Mid-America, is a railroad in the central United States, with its primary routes connecting Chicago, Illinois with New Orleans, Louisiana and Birmingham, Alabama. A line also connected Chicago with Sioux City, Iowa...

 Paducah

Paducah, Kentucky

Paducah is the largest city in Kentucky's Jackson Purchase Region and the county seat of McCracken County, Kentucky, United States. It is located at the confluence of the Tennessee River and the Ohio River, halfway between the metropolitan areas of St. Louis, Missouri, to the west and Nashville,...

 shops using a General Motors Electro-Motive Division (EMD) GP7

EMD GP7

The EMD GP7 is a four-axle diesel-electric locomotive built by General Motors Electro-Motive Division and General Motors Diesel between October, 1949 and May, 1954. Power was provided by an EMD 567B 16-cylinder engine which generated . The GP7 was offered both with and without control cabs, and...

, GMD GP7 or GP9

EMD GP9

An EMD GP9 is a four-axle diesel locomotive built by General Motors' Electro-Motive Division in the United States, and General Motors Diesel in Canada between January, 1954, and August, 1963. US production ended in December, 1959, while an additional thirteen units were built in Canada, including...

 as a start. It is similar to the GP10

GP10

The EMD GP10 is a diesel-electric locomotive that is the result of rebuilding a GP7, GP9 or GP18.The Illinois Central Railroad had three separate rebuild programs to upgrade their old EMD GPs and GPs that they had purchased from equipment dealers such as Precision National Corporation in Mount...

 and GP11

GP11

The EMD GP11 is a four-axle diesel locomotive rebuilt by the Illinois Central Railroad’s Paducah shops. It is very similar in appearance to the GP8 and GP10....

.

A total of 111 units were rebuilt to "GP8" for the Illinois Central and Illinois Central Gulf. Core units used in the construction of these units were Illinois Central GP7, GP9, a GP8, C&O

Chesapeake and Ohio Railway

The Chesapeake and Ohio Railway was a Class I railroad formed in 1869 in Virginia from several smaller Virginia railroads begun in the 19th century. Led by industrialist Collis P...

 GP9, D&RGW

Denver and Rio Grande Western Railroad

The Denver & Rio Grande Western Railroad , often shortened to Rio Grande or D&RGW, formerly the Denver & Rio Grande Railroad, is a defunct U.S. railroad company. The railroad started as a narrow gauge line running south from Denver, Colorado in 1870; however, served mainly as a transcontinental...

 GP9, DT&I

Detroit, Toledo and Ironton Railroad

The Detroit, Toledo and Ironton Railroad was a railroad that operated between its namesake cities of Detroit, Michigan and Ironton, Ohio via Toledo between 1905 and 1983.-Early history:...

 GP7, N&W

Norfolk and Western Railway

The Norfolk and Western Railway , a US class I railroad, was formed by more than 200 railroad mergers between 1838 and 1982. It had headquarters in Roanoke, Virginia for most of its 150 year existence....

 GP7, P&LE

Pittsburgh and Lake Erie Railroad

The Pittsburgh and Lake Erie Railroad , also known as the "Little Giant", was formed on May 11, 1875. Company headquarters were located in Pittsburgh, Pennsylvania. The line connected Pittsburgh in the east with Youngstown, Ohio at nearby Haselton, Ohio in the west and Connellsville, ...

 GP7, QNS&L

Quebec North Shore and Labrador Railway

The Quebec North Shore and Labrador Railway is a Canadian regional railway that stretches through the wilderness of northeastern Quebec and western Labrador. It connects Labrador City, Labrador, with the port of Sept-Îles, Quebec, on the north shore of the St. Lawrence River...

 GP7, RDG

Reading Company

The Reading Company , usually called the Reading Railroad, officially the Philadelphia and Reading Rail Road and then the Philadelphia and Reading Railway until 1924, operated in southeast Pennsylvania and neighboring states...

 GP7, St.J&LC

St. Johnsbury and Lamoille County Railroad

St. Johnsbury and Lamoille County Railroad was constructed in the 1870s as the Vermont Division of the Portland and Ogdensburg Railway to connect the Great Lakes with the seaport of Portland, Maine. The westerly connection with the Great Lakes was never made...

 GP9, SLSF GP7, and SP GP9.

The Paducah Shops also rebuilt 16 Conrail GP7s to GP8s. Nine were rebuilt in 1976 and another seven in 1978. The Rock Island

Chicago, Rock Island and Pacific Railroad

The Chicago, Rock Island and Pacific Railroad was a Class I railroad in the United States. It was also known as the Rock Island Line, or, in its final years, The Rock.-Incorporation:...

's Silvis Shops rebuilt 20 Conrail GP7s into GP8s in 1978. Morrison-Knudsen's Boise Shops rebuilt 13 Conrail GP7s into GP8s in 1978. The 1976 Conrail units rebuilt at Paducah were the equivalent of the Illinois Central rebuilds. The 1978 rebuilds were engine and electrical gear only rebuilds with no carbody modifications.

Reference

Data from Extra 2200 South Issue #93 pages 18-36.
Data from Diesel Era March April 2003.