Input from numerous forum members on another thread I started regarding the joy of driving a big six cylinder powered truck has spurred me to want to share information I have gleaned from a retired Ford Engine Development Engineer.
As you know, this engine became available in 1965 and was in production in vehicles until 1996. Some believe it was sold for industrial applications [generators, irrigation pumps, chippers, airport tugs, etc.] a little longer. It was never offered in a passenger car as was its little brother, the 240.
Towards the end of its production run [1980+], there were numerous prototype pieces manufactured and tested for the 300/4.9L engine. Ford does not release these documents and the general practice was to destroy all prototypes once testing was completed and the decision was made to not use this in production, so I want to list what was told to me as a lasting record. Any errors are on "me" as I am repeating what I have had the privilege to be told and am not at the technical level of the one telling me this.
Sometime [probably 1980-1983], a two barrel log intake manifold was made. It looked just like the 1 barrel manifold, but had two holes arranged parallel to the length of the log. This would have used a Motorcraft 2100 or 2150 carburetor.
Later, with fuel injection becoming available, "engine displacement management" was developed. Under ideal conditions [light load], cylinders could be disabled so the engine ran on less than 6 cylinders. This was to enhance fuel mileage.
Several engines were turbocharged. These turbocharged six cylinder engines had more power than the same model year 460/7.5L engines.
An iron crossflow head was developed for improved emissions and fuel efficiency.
All of the above were never put into production, however for a while, Ford did offer an aluminum billet head for drag racing only [no cooling passages] in their performance catalog for Comp. racers. The billet heads were milled out of a solid piece of high strength aluminum and were very costly - about $9000 bare. They were able to flow over 400 cfm.