Whoaaa, Nelly! Slow down a minute, pardner.
Some basics, first.
Is this a running, driving car, or a derelict you pulled out of a field somewhere?
If it's a runner, no need to dive that deep into the engine (at least not yet).
Start with an actual tune up- plugs, points/condensor, plug wires, cap and rotor, air filter, fuel filter, oil change and filter. Get good parts and not cheap dime-store stuff that cause as many issues as they solve.
Then get a good timing light and distributor wrench, and a tach/dwell meter; and start reading up on how to use them.
There is absolutely no reason to start diving into lifters, springs and rockers; much less intake and carb until you have actually established a need for them. 340s came with some of the best engineered parts ever available on a factory small block, and replacing major components willy-nilly will only lead to more issues and possibly a big step backward.
Don't worry about giving it "a bit of pep", once you've got it running well a 340 will have enough "pep" to scare you.
So, first things first- is this a runner or something that's been at the bottom of a creek for 20 years?