It's viable, but the argument is toast. Several rail lines used 6451, but the only rail line using that # and was close to accessing WP's line and Keddie was Southern Pacific.
Owner: Southern Pacific
Model: EMD FP7A
Built As: SP 6451 (FP7A)
Serial Number: 18135
Order No: 3160
Frame Number: 3160-A6
Built: 2/1953
Western Pacific only bought two FP7s. If you do a search of Keddie Wye images, you will see a ton of photos of these two workhorses: Their road numbers were 804 and 805. When the Zephyr was closed in 70, they were re-geared for freight and renumbered 915 & 916. 804 was wrecked in 5/72, and traded in to GE. 805 was also traded in to GE, then sold to Wellsville Addison & Galeton, then to
Louisiana & North West 49, then to Feather River Rail Society, in 1987. It's at the WP museum in Portola.
The vast majority of FP7s were toast by the early 80s, and 83 seems to be a landmark year for retiring the remaining fleet. But, by then, UP had absorbed WP, and SP had sold their 6451 to Amtrak years prior. In fact, they sold 14 FP7s to Amtrak, which remained with UP road numbers and paint until around 1975, when they were all converted to Amtrak paint and road #s (AMTK 110-123). 6451, by 1975, was repainted and renumbered AMTK 115-1.
Here are some pictures of these engines during the transition from UP to Amtrak paint- unfortunately, the only photo of 6451 is prior to the new paint and number.
Since there are no other known railways using the number 6451 that could accidentally run on Western Pacific lines (and several railways had access for runs or detouring- Great Northern, Union Pac, BG), and 6451 was retired by 75, it kind of kills the possibility that 6451 is a locomotive. Here's a list of Western Pacific's
stock and numbers. A list of Union Pacific
stock and numbers- including the sale to Amtrak of 6451. And a list of the WP stock and what
happened to it once UP took over in 83. Here's a
great little article detailing the rise of Western Pacific, Arthur Keddie's dream route, and some more stock info.
Here's a map of Western Pacific's rail system, and one detailing how it interacted with other lines- including the Inside Gateway ("Highline") that connected Keddie to the great Northern line in Bieber (which goes straight through to Klamath and points north and east)

Perhaps railfans can help with this, but I unfortunately think the locomotive idea has nearly bottomed out. When I began last night's post, I thought 'train' was the answer- then I made the mistake of researching it further. (There is
BN 6451 which ran with
Burlington Northern sometime during the 70s and possibly until 84-there are
photos of it in 82. Burlington Northern did occasionally come through Keddie, so more research on BN 6451 is warranted. There is also Conrail's CR 6451 that was running back then, but Conrail is mainly NY/NJ and only goes as far west as Illinois.)
Back to the original info on 6451, and whether Phillip mistook the window sill for the water heater. The first hurdle is believing Phillip, which I don't. He stayed the night at cabin 28 in January 81, according to LE reports, so he would have slept downstairs in Johnny's room. Even if that was the only visit to 28 in his life, it gave him an inside and out perspective of the cabin, including the entire basement and where the heater was. Plus the idea of him hiding down there makes no sense because if the killers were looking for anything, they're going to head to Johnny's room. Downstairs. Where he was supposedly hiding. From the killers. Who he caught a ride into Keddie with. And a ride back to Gansner Field with. Right.
As for the origin of 6451, the only reference I'm aware of that we have access to is the "Persons of Note" file in which, listed by James Seabolt Sr, is the following notation:
"found #6451 on window sill where John used to sleep"
How recent was it? Pen? Pencil? Scratched in? There are three windows in John's room, all of which were squeezed together in one panel and faced southwest towards the garages at the back of cabin 13-14. You're not going to see any license plates from that POV. The only other outside wall from Johnny's room faced the back yard, but had no windows and was further obscured by the rear stairs. I really liked the rail idea, but I'm back to phone #, partial license plate, or something else entirely.
"Back off, man. I'm a scientist."
reach me at
keddie28 AT gmail DOT com