318 cylinder head

your 318 with the stock cam, cannot use the flow-potential of the big valve heads. and between the compression loss and the slower-moving airstream, I've never had good results with this, And even worse if the gearing is in the basement. Yeah the smoggers are even worse.
Ok, the top end might have potential, but the bottom end sucks. So if you are prepared to throw more stall and gears at it, you can fool yourself into thinking your car is faster, but until you change the cam, it's just the same old Dart with gears and stall.
So if you are gonna go down this road, get yourself some zero to 60 time trials, before and after, the head change, and smarten me up. Remember; NO other changes are allowed. After that's done, you can do whatever you want and document the change in zero-to 60 as you go.

When you're all finished, add up all the money you spent, and all the time you spent, and decide if the Change in zero-to sixty was worth it.Only you can answer that. As for me, the answer was no.
So after doing that twice;
on the third time
I installed a 2800 and 4.30s, BadaBoom!. Never looked back. Even the smogger is now fun.
Whatever you decide;
Happy HotRodding.