Wow, Bruce, what a cool "sleeper!" Looks like you had the right combination of parts, if that thing would actually run 13's with a 260.
Most bone-stock 340 Dusters I saw at the strip ran 14.40s - 14.60s, on street tires with closed exhaust. Put some slicks on them, and add headers and they'd go into the 13's... Add a 4.10 or 4.56 gear and they'd run low 13's, maybe dipping into the high 12's on occasion.
At least, that's the way I remember it, but it was over 35 years ago, so I can't guarantee the veracity of any of that.
I've slept since then...)
In 1971, Ma Mopar swapped a 750 Thermoquad for the smaller, Carter AVS they had been utilizing, and I think they picked up a little on the carb change. But the next year ('72) they lost a lot of compression and dropped the intake valve size from 2.02" to 1.88", and I'm sure that didn't make them any faster...
How do you post a picture to this site?
Bill