i have a 300cid [4.9L] Inline six ford ..
very long build on that engine .. 23-25 years last time i tried to figure it out ..
as i have said before on this forum to derned bad ford did not get market acceptance back in '77
or then again maybe there was some other glitch..
had this been an option on my custom i would have selected it
in 77 ford had a tricky little solenoid valve set up ,,
see this article
i wonder if the current dual displacements have similar technology
ford dual displacement January 1977
Popular Science - Google Books
opportunity lost