Are 340’s rare

Yours ran a lot better than mine.
Had a 69 Dart I owned in 1972 and 73
Had 3.55 gears and cheapy headers.
Best I got out of it was 14.23@ 99 mph, which was a hair quicker than some others back then that ran mid 14’s.
Suspect it was little better gear and the headers.

that out of a 69 340? my valiant ran 14.2's all day long with a stock 79 360 long block with a performer intake and 600 holley being choked down by 273 manifolds. 3.55 gear too..