Combo opinions...

I say don't get the big valves. First of all, you would have to notch the cylinders to prevent valve shrouding. Second of all, you wont need that breathing capability with this budget build.

Porting will be helpful if you don't go overboard.

Stock 318 manifolds just plain SUCK. Get rid of them, they will hold you back. There are a few options for headers to choose from. they will really help the teen over stock manifolds.