jomichael-
If you really want to keep a stock look stick with a 305 or a 350. If anybody asks just tell 'em it's a 265 (wink, wink, nudge,nudge...)
Although I am not familiar with prices in your area, I will tell you that I paid $100 for a complete and running 305 and $200 for a complete and running 350.
By complete I mean with all power accessories, brackets etc. in place.
Parts wise you can find anything you need in the P.A.W. catalog and many others. Many times 350 parts are cheaper because they are more common.
If you want more of a Hot Rod - by all means go with the Big Block! As they say there is no replacement for displacement. Again, parts are available for the 396 and the 454, with the 454 parts being cheaper many times. Around here a 454 usualy sells for about $400.
Regardless of your choice small block and big block chevys are some of the most popular engines on the planet - and they both have their virtues.
Good Luck with your project!
Guy