Not disagreeing at all, Willowbilly ... as I am somewhat of al old "Ford Man" as well. (Ford partsman for 14 years, starting in 1979)
As I said earlier ... the 351M/400 was, IMO, a temporary powerplant stuffed into pickup trucks starting in 1977, discontinued in 1982. These engines fell victim to EPA regulations. Compliancy required, IIRC, retarding the valve timing 2°. Horsepower and fuel economy both fell off as a result.
As you said, they also had "engine management issues" which included overheating and detonation problems. The "fix" was a re-curved distributor that was issued on a "Campain" near the end of the life-cycle ... 1981-82.