With regards to the North Carolina Transportation Museum, they already HAVE an Amtrak F40PH, as I'm sure you already know. So does the California State RR Museum. I believe the plans are for both to be eventually preserved indoors, as seen in the NCTM artist's concept drawing.

Right now, the problem is that an F40PH or two preserved for mainline operation is going to run into two major problems: first, no one is really even thinking much of running any mainline excursions except under the aegis of Amtrak, who will provide their own (more reliable) motive power; and second, the F40PH's are nowhere near old/attractive/interesting enough (YET) to attract anyone trackside to see them go by, let alone encourage folks to go ride behind then and then sweat over them like they have done with, say, Baldwins, Limas, BR Deltics and Westerns, DB V200's, or EMD E's and F's. And unless you're planning a truly high-speed run with modern HEP equipment (say, a regular run from LA to the Grand Canyon or from NYC to The Greenbrier), there are typically more fuel-efficient ways to get that excursion train around. (Hey, at least Deltics can be run on one 1650-hp engine rather than both!)