No factory pistol grips in A-bodies, as far as I know, which kinda seems odd.
Shifter swap may indicate other changes from original, which may or may not be a factor for you.
Heck yeah, 340 Dusters are desirable, especially with 4-speeds.
Many feel that '71 is the best year, but '70s have a fan base for sure.
Check the spare tire well & rear body panel below the tail lamps.
Post some photos if you can.