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.