If the valves are "toast" as you say, you're wasting your time trying to get a smooth idle. The carb can't handle a fluctuating vacuum signal like that.
The heads will fix the idle, and run smoother, but if the rest of the engine is worn badly, it could turn into a smoker.
I wouldn't waste the new lifters on an old cam. If the engine is that bad, it needs overhauling. If you are really low on cash and need a beater badly, the heads might be worth a try, but don't sink a lot of dough into it.