318 running rough and losing vacuum when in gear.

yes, he is using it to rebuild for another car he is doing. wouldn't part with it. I traded a 1971 buick skylark to him for the dart. I"m not into GMs I only bought it because it was a good deal. I like Mopar. I have a 66 2dr polara and a 55 dodge pickup also.
if it were out on mechanical timing would it smooth out with increasing rpm?