340 actual horsepower

I doubt these factors are still current, as not too many people currently run 340's in NHRA Stock Eliminator classes, but here's a few factors from back in the day:
1970 340-6 Bbl. 325 hp E Stock
1971 340-4 Bbl. 320 hp D,E,F,G Stock (w/Thermoquad)
1968-70 340-4 Bbl. 295 hp F,G Stock (w/AVS)
1972-73 340-4 Bbl. 275 hp G,H,I,J Stock

In most cases (except the 440-6 cars for some reason), the NHRA factored Mopar engines at a higher output than their advertised output. Horsepower numbers before 1972 were pretty much advertising propaganda, and seldom reflected actual output. Beginning in 1972 the SAE "net" ratings were mandated for all cars sold in the US, which were supposed to reflect output "as installed".