from what I have read, stock 68 383 roadrunners ran anywhere from 15 flat to 15.30’s
i had a 69 Dart GTS 340 in 1972. Came with 3.55 gear.
I added cheapie headers. My first drag strip pass in my life was in that car
went 14.23@99 mph
quite a bit faster than the BBody 383 cars, even allowing I had headers and glass packs