On carb size, Too large - you will loose bottom end power. Too small - you will loose top end power. Try to ge the best of both worlds. IMHO 390 to 500 CFM will work for your street application.
Stock style (made in china) ram horn 2 1/2 inch manifolds from DORMAN (see link) will work pretty good for a street app. at $64 each delivered.
http://bbb-carb.com/Exhaust_Manifolds.htmThe key to any real performance build is building the engine and matching it to your vehicle weight, tranny and rear end ratios as well as vehicle use, as well as really "building" your engine (see books by David Vizard). With some minor modifications you can see some minor differences in power gain. Without proper tuning you can also see some power decrease. And then again, some minor improvments can be hard to distinguish any power increases.
If you want to see some improvments, study your vehicle and your ideas of what you want for performance out of your vehicle and spend you money wisely the first time. Bolting up parts that say perfomance is the most common mistake people make. You have bragging rights to the parts you place in your engine, but that doesn't always transfer to any bragging rights at any finish line.
I think a majority of people could make some realistic improvements with an RV cam, small 4 barrel carb (500 to 600 CFM), and some stock type 2 1/2 inch ram horn exaust manifolds or hugger headers.
If you wanted to spend some more money, go with some vortec heads. Remember that vortec heads also need other parts to make it work such as valve covers, intake manifold, plus other small parts to raise the price a couple of hundred.
Good luck with your choices.
