Steinbrenner was fined $15,000, suspended from baseball for 15 months by Commissioner Bowie Kuhn, and later received a presidential pardon from Ronald Reagan.
The FBI has released 400 pages relating to its investigation of Steinbrenner. You can download PDF files all of the documents here. A description from the FBI:
This release contains three files: 1) the FBI's investigation (Headquarters File 56-4737) into illegal campaign contributions made by Steinbrenner and his company, the American Shipbuilding Company, to the Nixon presidential campaign; 2) a laboratory analysis for the Federal Highway Administration of several anonymous letters concerning possible fraud in the federal aid highway program in Ohio (Headquarters File 95-189353); and 3) material related to Steinbrenner's appeal for a pardon from his conviction for illegal campaign financing and obstruction of justice (Baltimore Division File 73-841).