Made it home!
First day: 2:00 p.m. from Ogallala NE to the middle Iowa, where just before midnight the engine developed a quiet howling noise that stayed. Slightly higher pitch than the engine and it raised/lowered and engine rpm raised/lowered, but got much louder as engine rpm increased. Got to my Wallyworld parking lot for the night around midnight MT. Coolant reservoir was slightly low so I topped that off. Let it cool off to see what the morning brought.
Second day: should have changed the oil & filter as I reached the 500 miles recommended, but with the howl, I was hesitant to change something given the howl, which returned and mained as soon as I was warmed up. Limped along, without the same acceleration, stopping often to check under the hood for clues. Around sunset, with no luck determining the source of the howl, I finally decided to change the filter (carquest/wix), although still hesitant on the oil. Changing the filter removed the howl... Also brought back the acceleration. Suspect the rare-earth magnet stuck on the end of the filter may be involved. Fine to change the oil. Continued on to Chicago and past, stopping at midnight MT, at a service area on the toll-way somewhere.
Third day: awake, so start driving around 4:00 a.m. MT, spending 20 minutes at one stop talking about Eagle engines with a father whose son is about to rebuild his Eagle engine. Lost an hour trying to find a working pay phone in Watertown NY. Cross back into Canada before my U.S. medical insurance expired at midnight, making it home just before midnight ET. Dropped the trailer at a local business where I'm known, and home to bed. Engine has much more acceleration (looser?) after its run back home.
Up for a while this morning, then energy crashed. It'll take a few days to be back to normal. Have to go retrieve and unload the trailer, then it'll be back to bed.