Add hotter cam or Add hotter head ?

Per sake of the discussion, let's say the car is a '72 Duster, 318 with and addition of 600 eddy carb on a performer intake and 2.25" duals ran out the back from the stock manifolds. The car has a 904, and 3.23 gears. All in good working condition.
*WHAT MOVES THE CAR QUICKER IN THE QUARTER MILE?
- A hotter cam, any cam and lifter kit you can buy or have custom ground.
- A hotter head, any head is the option including trick flows.

- no other changes to the car can be had.
Depends on what cam is in it now and what future plans may be in the stew pot. With stock heads the cam choices are restricted some. I would think go with a cam, even if the heads are the choke point. Then later the heads can be dealt with. Uncle Tony is doing up an engine using mostly stock parts. Yes, an aftermarket cam. Valves are being replaced in factory casting heads. Porting with DV and Unity Motorsports involvement. They are using the Carter 2 barrel carb also, so the build is a bit like a restrictor plate engine. Aluminium heads not allowed. Will be interesting to see the results as head work vids come out and the final dyno result.