Hey man how's it going? You might wanna go introduce yourself in the Introduction forum so ya get to know some of us first before ya go poppin' off questions, haha. Since everyone is going to tell you to use Search, i'll help you out a bit!:thumbup
One of my favorite cheap seat-of-the-pants power increases, is to simply advance the ignition timing. It's all free power. You can go as far as you are comfortable. Keep an ear out for detonation or "knock" if you go too far and dial it back a bit.
One indication that you are getting there, is when you stab the gas the engine rpms spin right up. With retarded timing you stab the gas and the revs are slower coming up. Check it out.
a stock 351w has around 210hp and 315ft/lbs...somewhere really close to that. I don't know if ford measured that at the wheels or flywheel.
Cheap hp...that is funny...but if your serious about it....
Start with redoing you WHOLE exhuast. Get some nice shorty headers, replace that restrictive y-pipe, ditch the cats if you can or go high flow ones, and get free flowing mufflers....thats gonna be about 500 for all of that. Probably get a noticeable power and gas mileage increase.
Also make sure your motor is tuned up good(actually, you shold do this first). Get new plugs, wires, cap, rotor, nice ignition coil. Then open up the plug gap a little and bump the timing up a bit. Should give you better gas mileage and throttle response and restore some lost power.
If you want big HP numbers, your gonna get more expensive, look into aftermarket heads, or iron gt40s.