Me thinks talking about the 383 in the A body GTS vs any 340-360 would be the discussion. Me thinks the 383 was heavier and dint really perform any better in that particular a body. But I am not 100%., plus add in that the 383 didnt have power steering etc the trade off wasn't worth it. Speaking in terms of a street car.
the suspense was killing me so I did a quick google:
67 dart GTS 383 1/4 mile time 14.9 at 93 MPH.
68 dart GTS 340 1/4 Mile time 14.8 at 94 MPH.
Bot were 4 speed cars. I wanted to make sure I wasn't posting BS :)
Website is called
Automobile-Catalog the Catalog of Cars, Car Specs Database