New to V8's. 340 or 383?

For what it's worth, I would never consider a 383. If you're going big block, go big, 440 or more since you'd be buying everything from scratch anyway.

Same usually goes for small block. Unless you have an engine to build already, go 360 as the other parts are pretty much the same price as is machine work. As previously mentioned, 340 block will cost more. I happened to come across a good deal on a nearly new 318, so that's what I'm running for now. Sometimes it depends on the deals you come across at the time you're looking to do something!