Hi. Im 15 and I own a 1971 chevy nova. Originaly had a in-line 6 with powerglide. I want to make it a car that can be driven on the street on high octane pump gas. I have a 400 chevy engine but need help with what i should do with it. I want an engine that is loud and lopey with a rough idle. Need help on cam/intake/carb/ pistons/heads. I would like to have around 400-425hp. My friend owns a garage and will work for no labour charge and can get parts relatively cheap. I own a 350 turbo and am looking toward a 3000 or 3500 stall conv. The rear is my second biggest problem. It is a stock 10bolt, 3.08 ratio. I would like a posi and dont want to spend $500 on making it one, someone mentioned about just welding the spider gears together, Is this a good idea? And will the 10 bolt hold up with a posi? should i have a lower ratio? I plan on putting about $1500 into the engine which I already own. What kind of combo could i get for it so it will get 400-425 hp?
Any suggestions would be apreciated. Thanks-Caleb  

I would use a .470 or .480 lift crane energizer cam kit with a summit stage 3 intake and a 750 vacuum secondary holley carb and a rebuild kit with hypereutectic flat top pistons, moly rings, hi-volume oil pump, felpro gaskets, federal mogul bearings,double roller timing set and brass freeze plugs and a good set of headrs.For the heads what is the casting number on the heads you have may be you could port and put bigger valves like 2.02 or 2.05 and a 3 or 5 angle valve job on the heads you have instead of buying a set of aftermarket ones.