bit of a braindump... Hard to get more specific without more specific requirements...
Is this a drag car, track car, street car, daily driver, etc. Basically this will lead you to - where do you need power and how much do you need. "Speed costs money, how fast do you want to go?"
Just about everything is a balance of top end power vs bottom end power. For most cars, you will aim to midrange to get the best overall. Drag cars will aim for all top end. Trucks/larger vehicles will aim for more bottom end.
some general conditions...
to move the power down:
longer intake runner
smaller ports in the head and manifolds
These help to accelerate air flow at lower RPM, but choke it out at higher RPM
to move power up:
shorter intake runners
large port head
cam with big lift/duration
Typically when you are buying parts (especially cams, heads, intake) it will say what range it will focus the power. You want to try and match all of these together. Parts need to work together. Having a big valve head with an intake or carb that can't keep up isn't going to work. Likewise, if the ports are too large for the RPM you are aiming for, power will suffer. The engine is a system, if all the parts aren't tuned together, it is not going to perform its best.
Parts such as the carburetor, and ignition just need to work correctly. Carb needs to be sized properly and TUNED. EFI is nice, but takes a bit of work to hook up. Typically has data logging, so very useful for exact tuning. Depends on your goals if you want carb or EFI.
stroking and boring should add power all around as they increase the displacement of the engine.
Forced induction (nitrous, turbo charger, supercharger) is going to give you the biggest bang for your buck if your looking to make BIG power (500hp+)
While you are in there, you want to be sure to cover all your standard rebuild items first - gaskets, bearings, oil pump, timing gear, etc. DONT CHEAP ON HARDWARE. go with upgraded rod bolts, main studs, head studs, stronger rods and pistons.
If you are really interested in building a SBC, there are hundreds if not thousands of books published. SBC is one of the most common engines in the race world. They sky is the limit on aftermarket parts. People have been racing SBCs for over 50 years now. Hit some forums, car clubs and shows, track days, Friday night at the track. See what other people have build, how it runs, what works, what doesn't, things they have learned.
If the sky is the limit, your going to be working with a top level professional and building top dollar engine, not rebuilding some old engine with advice you got from people on the internet...