Flywheel

You didn't say what engine you want the flywheel for and you seem to have a number of different engines so it's hard to tell which. But if it's not a 360, which uses and external balance flywheel, but a 318/340 you wont have any trouble finding a flywheel. Just need 130 tooth flywheel for 10.5 inch clutch. If it's the 383 big block you're talking about, not sure whether they are internal or external balance engine (internal I think). But in any event why dont you just ask your engine builder, after all he will be balancing the flywheel with the rotating assembly.

Aside from Summit and other suppliers, I've seen some decent deals on steel SFI approved flywheels (smallblock internal balance) on ebay. I bought my aluminium flywheel off ebay as a second hand piece, but it'd never been used only bolted up to the engine, so I got a really good deal there. Once you know what you're after have a look around.

Throw-out bearings are all the same for any particular engine. Which pilot bearing you need depends on the engine/crank and whether you are changing over from auto to manual because some crank ends used in auto cars where not fully machined to accept a pilot bearing.

Again, not enough info provided to be more specific.