One or Two Breathers

In addition to the above issues, expect excess sludging in the engine over the long term without a PCV and typical street use. And moisture that accumulates inside will add to the acids in the engine and increase wear rates. BTW, older engines from the early 60's and before had a breather AND a road draft tube that exited below the engine; the draft tube would get a vacuum pulled across the lower end when the vehicle was moving and so would suck some of the crankcase vapors out and prevent pressure induced leaks, etc. So running with just breathers is like going back to the 1920's or earlier in terms of crankcase ventilation....LOL

As for the PCV to use, you may not want the original 318's stock metal Mopar PCV if your cam is moderate. At stock idle vacuum levels, the PCV will close down some to avoid putting excess air into the intake and leaning the mixture. But the stock Mopar ones from the 60's/early 70's will open up to the cruise airflow level even at the lower idle vacuum that you get with a moderate cam; that will cause idle problems with too much air. There are PCV's that are designed to close down their air flow properly even with lower idle vacuum levels: Fram FV191 is an example.