You're on the right track, but the REO trucks built in the 1950s were gasoline only. REO was defunct when the LDx-427 and 465 multifuel engines were introduced. The multifuel trucks were built in the old Studebaker plant under Kaiser Jeep and American General brands. But it was in fact the REO designed chassis the multifuel engines were going into.
MAN designed the multifuel combustion process and licensed it to the companies building the multifuel engines under US contract: Continental, Hercules, and White.
The important thing to keep in mind, the engines were designed to run on leaded gasoline, which had more lubricity than unleaded. Gasoline will shorten the life of the injection pump. Other than that, there is nothing else involved. You can mix fuels in any ratio, and timing does not change. You only get less horsepower from burning gasoline. The LDx-465 model had a fuel density compensator which would try to remedy the horsepower loss, but this was later disabled on the D model, I think to meet 1980s emission requirements.
This Popular Mechanics article explains the multifuel combustion process better than I can:
link
I was not aware of the Rolls-Royce K60 multifuel, I will have to do more research on that. I own four LDx-465s, three in trucks, and one spare.