You could spend as little as 500 or as much as you want, it all depends on what your gonna do, keeping it stock and buying cast pistons will be way cheap if your gonna reuse your rods and crank.

cam and lifters -120 summit
gaskets-40 felpro summit
timing chain- 35 true roller summit
heads- all depends on whats done to them
pistons- as low as ABOUT 15 dollars apiece for cast
block-all depends on machine shop but approx 250 to hot tank bore, cam bearings, freeze plugs.

Since its a chevy bottom line is it wont cost much to run great

i would recommend the how to rebuild your small block chevy book to help your rebuild.

thats just a estimate on the main stuff if your gonna reuse your intake, carb etc.

good luck