Number 666 was built in July 1955 as UP E9B 963B (c/n 20503), leased to Amtrak as number 1463 in May 1972, sold to Amtrak becoming 463 in November 1973, retired by Amtrak on June 16, 1974, rebuilt by ICG-Paducah to unpowered Amtrak steam generator car 1916 in late 1975, renumbered to Amtrak 666 in mid 1977. It was sold to Alaska Railroad in January 1982 becoming ARR P6. (Note: The current UP 963B is actually the original UP 970B.)

Number 667 was built in October 1955 as UP E9B 971B (c/n 20511), was leased to Amtrak in May 1972 as number 1469, sold to Amtrak in November 1973 becoming AMTK 469, retired by Amtrak on June 19 1974. In 1975 was rebuilt by ICG-Paducah to unpowered Amtrak steam generator car 1917, renumbered to Amtrak 667 in mid 1977, sold to Golden Arrow Tours in May 1983.

Number 668 was built in May 1954 as UP E9B 952B (c/n 19288), leased to Amtrak as 1456 in May 1971, sold to Amtrak becoming 456 in November 1973, rebuilt by ICG-Paducah to an unpowered steam generator car 1918, renumbered to Amtrak 668, sold to Providence & Worcester as number 51 in April 1983.