BTW, the list above for 'good' parts is about $15k plus machine work for a conventional headed BBC. Assuming you buy off the shelf parts. the best bargains on new stuff is definitely the crate motor route from places like RM or Shafiroff. Be careful though because the advertised priced are usually with the cheap stuff (Chinese crank, off brand lifters, etc) that you DO NOT want. To get one with a Callies or better crank, oliver rods and good lifters will be about $18-20k
Honestly, the best way to get a good engine cheap is to buy a used high dollar engine, like a 14 or 18 degree engine, and freshen it with new rods, pistons, rings, bearings, valve springs, valves, etc. You can pick up a really nice 598 or 632 Big Chief/Duke engine for about $12k and spend about $6k on it to get a solid engine that would have cost minimum $25-40k to build from scratch. That is the route I was going until I got a great deal buying a conventional headed 555 that I built a couple years ago for a friend. Could not pass it up.