The 340 engine is considered one of the best muscle car engines of all time. This article gives a great recap of its history. Ultimate Chrysler 340 Engine Guide - The Giant Killer 340 (musclecarclub.com)
My cousin had '68 Barracuda convertible with the 340. He swears he was blowing away Corvettes with it. The car is now in pieces awaiting a rebuild after many years of storage.
I had a 69 340 4spd Dart. Despite a brief search I was unable to find one true stock motor dyno on any 340. Anything noteworthy on the streets at that time wasn't stock. The streets were dominated by performance machine shop owners and their customers who ran the spectrum of modifications.
The 340 4-barrel was purposely under-rated at 275 hp. to give it a competitive edge at the track and the avoid high insurance surcharges. The NHRA, however, quickly caught on and factored the horsepower to 325. (Note- Chrysler stopped taking dyno readings at 5,000 rpm instead of its 6,000 rpm redline). Being 95 lbs. lighter than the 383 (525 lbs. vs. 620 lbs.) and only 10 hp less, it made the perfect choice for a great handling 'Cuda or Challenger (Note- It was a $45 option in 1971. This is $362 in 2024 dollars).
