Yes 340 , or it also could have been an optional upgrade from a 7-1/4 rear on a 318 or slant six car.....The easiest way is locate your broadcast sheet to see what your car had in it originally....usually under the rear seat in under the seat springs.....To see if your car was a 340 car or not just look at the 5th digit of your VIN number....if it is the letter H it had a 340 in it from the factory......If it is a letter G it was a 318....a letter C there would indicate a slant six car.....
