cheap performance mods?

[sweatmachine]

I have a bone stock '78 heavy half, 350 w/ 4 barrel, and just before I got it my uncle installed a new stock spec cam.

It has stock (or at least really quiet) exhaust, no cat, and stock air cleaner.

1. How much hp could I expect to gain from opening up the exhaust and air filter, and rejetting the carb to match?

2. Exhaust: I can weld, and have all the equipment. I was thinking of welding up my own system. What muffler should I go with? Loud is ok.

3. I've messed with a lot of motorcycle carbs, but never a carb on a car/truck. What adjustments/jetting should I expect to need?

Thanks guys!