New to V8's. 340 or 383?

Hey guys I've had my slant six Duster for 10 years now but I just recently bought a 67 Barracuda fastback with a 273 commando. The car came with a SBP 7 1/4" rear and 10" drum brakes. I plan on swapping the rear for at least an 8 1/4" and the fronts to discs.

I've just began researching V8's but I've always wanted a 340 ever since I was a teenager. My question is, how much can I expect to pay to get a 340 and just have it rebuilt to regular factory specs? I'm not interested in racing it so I don't need performance mods or anything. I just want a nice looking car that looks like it could be original. If I buy a 340 block for $500, how much can I expect to pay for heads and to have it rebuilt? I'm just looking at ballpark here.

Some of these Barracuda's came with 383's so I've been wondering about those as well. They almost seem cheaper than 340's. What's a ballpark number as far as buying one and having it rebuilt?

Also what are the pros and cons of a 340 vs. a 383 in this car? The 340 seems like it would just drop right in. Are there certain mods needed to drop a 383 in or would I just need different motor mounts since some cars originally came with them? I'm a total newbie when it comes to V8's so I apologize if I'm asking stupid questions.