well, we got to start comparing somewhere.....This is what they gave us, 'cept the 340 was slightly underrated from many sources, closer to 350HP with only headers added to a ~320HP baseline.. "..
On factory claims of 275 horsepower at 5,500 rpm and 340 lb-ft (3,200 rpm), we got 320 horsepower at 5,500 rpm and 368 lb-ft at 3,500 rpm. So it's clear Mopar understated the facts by 45 horsepower and 28 lb-ft. Then we replaced the manifolds with a set of headers and got 352.1 horsepower and 395.9 lb-ft (at 3,200 rpm)—77.1 horsepower and 55.9 lb-ft higher than published peak claims."
https://www.hotrod.com/articles/bad-mopars-340-beat-ford-chevy-shocking-new-data/#:~:text=With the single four-barrel,320.3 horsepower at 5,500 rpm.
Oh and about that 360 smogger motor....."
Speculation in the dyno room placed expectations on the stock 360 at around 180 hp. The 360 shattered that assumption, and belted out a solid 266.2 hp at 4300 rpm, and a stout 371.3 ft/lb at 3300 rpm. The lowly 360 had some guts after all...The 360 liked tube headers, with power moving up to 276.9 hp at 4200 rpm, and torque jumping to 390.7 ft/lbs at 3200 rpm...After we bolted on the Edelbrock #1904, (original numbers were from a TQ) we got 276.8 hp at 4500 rpm and 377.1 ft/lbs of torque at 3300 rpm (...and thats with a stock 360 252/.410 cam!.."
Dyno-Test 360 Smog Motor - Mopar Muscle Magazine