well im 16 years old and i have a malibu 72 307 but i have a 350 4 bolt i want to restore but i dont know wich parts i have to get to it new to have better performance i know that the cilynder heads are important but i want to put it all but with low budget i want it to run like 400hp

Cool another kid made it past the import gaunlet!!!Glad to see your interested in real cars!!
I remember being 16 and confused about cars ,i took an r.o.p class in autobody & automechanics for two years.THIS IS SOMETHING I SUGGEST IF YOU HAVE CLASSES IN YOUR AREA.
Another good way to learn is to subscribe to all the car magazines ,They do have some good advice.

As far as choosing parts ,i would suggest ordering a PAW catalog i call it the (bible) in my house.They have all kinds of parts and give you good technical advice on the parts!!!! ( performance automotive warehouse)
I would suggest staying around 325-350 hp as a beginner,400 hp is alot to handle when you first get your license!!
Keep reading some threads and they should have good advice as well.

The GM Vortec heads are good option and produce good power and torque

Aftermarket Heads, a 262 or 268 cam, rpm intake, headers, 2.5 exhaust, 650cfm or so carb and you will be more than happy.