You obviously have more specific knowledge on this engine than I, but I distinctly remember from back in the day that Ford developed the SOHC for drag racing and the DOHC for endurance racing. This is all I could find at the moment.
"In 1964, Ford had their best season ever, with 30 wins. Dodge was second with 14, while Plymouth had 12. Adding the five wins that Mercury had, the 427 had a total of 35 NASCAR Grand National wins for the 1964 season. Fred Lorenzen won the Atlanta 500 and proceeded to beat Dodges and Plymouths, which were using 426 Hemi engines, in six of the next seven races. Ford was using the high-riser intake and matching heads, which were allowed by NASCAR for one season (1964).
In 1965, NASCAR banned Ford's high-riser engines
[4] claiming they did not fit under "stock" hoods, allowing Chrysler to continue racing its 426 Hemi, which had been installed in a production vehicle that year. Yet
[5] Also in 1965, Ford developed its own version of a hemi-chambered engine. The 427 "Cammer" used a pair of overhead cams to operate the valves in its hemi. NASCAR banned the engine. Then Ford developed the medium-riser intake and head, which fit under stock hoods and was accepted by NASCAR. Ned Jarrett, driving for Ford, was the 1965 Grand National champion and Ford won the NASCAR crown. "