Thank you for your very informative & interesting post
I don't pretend to be any kind of expert. But my memory is still reasonably sharp as regards Ford Clevelands and the reported figures they produced 'back in the day' as opposed to historical revisionism, eg:
Fwiw in 1971 a healthy 351C 4V Cleveland (aka 4-bbl) used to push a tad over 190 rwhp out the back end of an XY GT Falcon. How that translates into fwhp I don't know, but a race-prepared XY GT (owned by Jack Brabham no less, see pic) made 295 fwhp according to its specialist builder, and obviously a premier example. This is is a not inconsiderable 45hp less than the "340hp very easily" claimed above for your typical 351 4V Clevos - despite XY GT 351 engines being of identical specs (hi comp, closed chamber, big port) USA motors and yes at that time fully imported
Reputedly a carefully race-prepared Falcon GT-HO Phase Three (Clevo w/ Holley 780, upspec cam and OE extractors etc) made around 350 fwhp in Series Production trim - which is only 10hp more than this 340hp claim, for stock 351C 4Vs, in production trim with the Autolite 4300 carby!
I also recall 1971 quotage from a senior Ford-AU Executive in a drive-test of his personal XY GT-HO company car which did a genuine 160 mph on the Ford-Oz speed bowl through being modified by the factory race-team into 'Phase Three Plus' specs, that "she pulled 232 (rw)hp on the company dyno"
Another intriguing quote, this one from Allan Moffat's engine builder. Moffat was Ford AU's factory driver and #1 Cleveland racer through most of the 1970s, following his previous employ as contracted test driver & racer to the famous Kar Kraft USA. There would be few others who can claim to have been GIVEN a brand new Kar Kraft-built 1969 TransAm Mustang!
(Anyway it concerns Moffat's 1973 Bathurst winning Falcon which was flown over to the USA for rebuilding into his '74 Bathurst car by Kar Kraft, who farmed out the engine build to Kings Engine Services of Ferndale Michigan. The CAMS reference is to the Confederation Of Australian Motorsport, our governing body)
At about this time [1974] we also had an interesting development with King's Engine Services. The yanks had bragged on and on about the 351 Cleveland seeing 500hp with the stock intake manifold and an 850cfm square bore double pumper Holley carb. In Australia we could never squeeze out more than 400hp, and that was with twin 48mm DCOE Weber carbies.
Allan commissioned these guys to build an engine which we would compare with our home grown engine on the same dyno on the same day. Well, they screwed together their best killer engine, which did not meet CAMS [production] regulations due to bore size, head porting and manifold choice, and sure enough it made 500hp. They then fitted ours, which was CAMS legal, and it made 504hp!