The problem with these old Fox 302's is literally everything is a restriction on them. You really won't see a whole lot of benefit from changing just one or two small parts at a time. The real benefit is changing several in combination to get the best bang for the buck.
If money allows, this is the ideal time to change heads, since you'll have the car torn down that far anyway. Your future plans for the car are going to really determine how to pick the head. If its just going to be a basic bolt on, N/A boulevard cruiser, then most entry level heads will do the trick. If you're going to get aggressive with modification later on down the road, then you head choice should be on the more aggressive side as well.
Knowing this, along with what other things the car might already have done to it (since finding a stock one is pretty rare now a days) should be your first step.
Warning....these cars WILL suck your wallet dry if you let them!