I loved my '69 Charger R/T with 440. Put the petal on down some, not all they way otherwise you may sit in one spot for a second of two as you think about the next set of tires to use.... And just hang on. Now with that being said, there's a guy living around the corner from me, he's got a mostly original '71 RoadRunner with a 340 and 4 speed. As far as I know, the only thin that's not original on the car is the hood, don't ask, I don't know, but it's the correct style, it just says 383 instead of 340..... He says it's a blast to drive, he's rebuilt the motor and has a double pumper on there... Plus being a 4 speed, you don't have to worry about a torque converters stall speed. Whatever you decide on, good luck. I'd say it's a toss up. As you probably know, Chevy has there "350" and Ford has there "302" plus there new 4.6 in the Mustangs... Mopar has the "340" so...... Good luck, and have fun.