I have a 402 cid magnum engine in a 67 Barracuda with cleaned up stock heads that runs 11.20s with a mild hydraulic roller cam and 3.55 gears in it so you can definitely get high 11's in a Road runner I bet. You will be RPM limited with the heads though. I shift at 5800 and cross at 5800.

With a set of good aftermarket heads and more gear mine would run high 10's easy.