I think he was referring to what you said about '72 California emissions.

OH! Right. Missed that.

Best just to avoid '72 California intake manifolds.

Craig, my vacuum map on my '75 Dart is IDENTICAL to the one you posted above. I was not aware that dotted line meant "optional" until I saw your post...guess I should read my vacuum diagrams more closely! Maybe I do have an original air cleaner and I never had an OSAC valve.

On another (related) subject: in the lower left of that vacuum diagram is something called the charcoal canister. What does this do? Is this another piece of emisssions-era crap that I can remove?

Overall, which vacuum lines in that diagram are unnecessary emissions crap that I can remove to improve engine response?

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'75 Dart Swinger, bone stock 225, 1 bbl carb

It traps and stores gasoline vapor from the fuel tank and carburetor bowl, and release it on a metered basis to be burned in the engine. This is much better than what went before, when the fuel tank and the carburetor bowl were just vented to the outside air, to float off (carrying-off your gasoline dollars with them and stinking up the garage).
Well, you could, but it won't gain you anything. No improved performance, no improved driveability, no improved nothin'. And your fuel economy will drop (a small bit, but at these prices, every bit counts!). The fuel vapor containment system, which consists of the charcoal cannister, the fuel tank, the pressure-vacuum fuel cap and all interconnecting hoses and lines, is very much worth keeping in working order.