Many of the BN's inherited passenger F's went on to serve Amtrak, although Amtrak leased, rather than bought, most of them. Once Amtrak had enough new locos, the F's were returned to the BN, regeared and repainted, and put into freight service. Most of them ended up in Washington. In the late 70s, the Pasco roundhouse often looked more like the 1950s, with solid consists of F's, mixed with Alcos of many types, all in green and black. It actually looked good on them. It seems that all of the "oldies and oddballs" wound up there, and for good reason. The ex-SP&S shop crews knew Alcos, and the NP and GN folks in Interbay and Auburn had long experience with the Fs. Powder River coal, and other traffic, was growing so fast that the BN couldn't buy new power fast enough to retire the old stuff.
We moved to Kentucky in the summer of 1978. By the time I got back, in 1981, all of the old stuff had disappeared.