Same car at about the same shipping weight will go mid-high 10's today under NHRA/IHRA rules. But the rules today have allowed a LOT more stuff than in 68. Under the 1968 rules, it could be considered "Pure Stock" these days. The 340 was under-rated anyway.
That 109mph would be closer to low 12's if the car hooked well and had a better converter. MPH is a more accurate indication of horsepower.