We used a 268 Comp in my son's '69 El Camino 350. It was the most cam I'd let him buy with an otherwise stock motor and converter. I don't remember the idle rpm's, but I remember we had to idle it down pretty low to find the lope in it. The motor pulled hard from off-idle to 5,000. We used 12 degrees initial and 24 degrees centrifugal all in by 2,800 r's.