A good start with your stock engine would be a cam 10-15 degrees at .050" more than your stock one, good headers, a good porting job, and probably a little larger throttle body. You will most likely need to install a higher pressure fuel pump. And definately an aftermarket computer chip; I recommend JET. They do a lot of stuff with Fords. To get some specifics, you might want to contact Racer Walsh at racerwalsh.com.
Theres nothing wrong with the stock pistons etc. I have used them in many engines and put many hard miles on them. The only question is what your cylinder bores look like. If they are worn you will want to have your engine bored out and install new pistons. One thing that will actually enhance your hp as well as the survivability of your engine would be to have your crank, rods, pistons, flywheel, and balancer balanced as an assembly.
As for the heads, you could make the kind of horsepower you want usint the stock ones, but that would require a good porting job and I would also recommend at least going to 1.56 exhaust valves. If you want a bolt on head that will give you far superior breathing and is basically a 40-50 hp bolt on to your stock engine, go with the Trick Flow Specialties, Twisted Wedge head. You will be starting out with a head that flows better out of the box than you will get with working over your stock heads. The reason I recommend these heads is that on all other heads to run 2.02 intake/ 1.60 exhaust valves, requires either getting special pistons that are flycut for that big of valves or to have your stock ones fly cut. Due to the valve angles used in the Twisted Wedge head, this is not necessary, unless you go to a valve lift in excess of .540. I have a set of these on a 351 and am totally enamoured with them. Another plus is that they dont cost any more than most aftermarket aluminum heads and are less expensive than most, not to mention they out flow all but the most built out heads.
I still contend that you dont need a cam with more than about 210-220 degrees duration @.050" lift. If you go much larger, you will find that driveability may suffer, especially with stop and go in traffic. Consider that you will not be running your engine all the time at stratospheric rpm, and most of the time you will be running at max in the 2500-3500 rpm range. You can always over wind an engine but you cant underwind it. One major area of consideration would also be in your intake manifold. If you have the $$$$$$, go for a good aftermarket set up. The trouble is the after market intakes for EFI will cost you almost as much as a set of heads, when all said and done, and the factory intake will flow a lot better than it is given credit for.