I dont want to sound like a dick, but I speak my mind. I was young once too, and I have learned a lot the hard way so I want to pass on some wisdom that you can either take it or leave it. In my opinion, spend your money wisely in all the right places. A loud stereo and a snotty exhaust wont get you very far other than attracting the popo, thieves and fat chicks. Set yourself a budget of $1200. Personally, I would invest in good brakes, Spicer U-joints, a good rebuilt carburetor tuned up properly, Warn hubs, and a decent set of used Mud Tires. Save up for a used Warn 8274 Winch. Make sure all your lights work, a good battery and alternator including cables and battery clamps. Like Rusty Nail said, Please... please get a Haynes shop manual and read it.. twice. That old square body will teach you all the essentials of pulling wrenches, skinning knuckles, building character, making you a man and life in general. It has seat belts... use them. Change oil religiously and wash the engine and underneath. KEEP IT SIMPLE, nothing wrong with stock replacement parts. A dual friction clutch and headers on your truck is like a boob job on a midget (no offence). Invest in a good multi-meter and a torque wrench. Learn how to use them. Set your timing with a vacuum gauge.
Take care of it and it will take care of you. Besides, Country Music sounds best on a factory AM radio. Any hoe can dig a sub, but a good woman loves a guy with an AM radio. Dude, you are 15. I would gladly trade places with you with what I know now.
Hope this helps. ~ Rusty