well, my 496 bit the dust via a roller lifter that committed suicide and put metal all through it. So its going to the machine shop this saturday for a freshening up, a good cleaning, new gaskets, new bearings, new rings. Anyway, just machine work, you doing assembly all yourself, assuming a valve job, bore & hone, blah blah blah, is gonna run in the 500-700 range, depending on what kind of deal you get.
Big block parts are also pretty expensive, a higher quality set of pistons will be in the 4-500 range. Im not a person you want to talk to about a budget build, I have ~$8k in my engine, but it does have all the non essential goodies, 4340 forged crank, 4340 H-beam rods, blah blah blah. Anyway, being that vintage, do you know if you have the peanut port heads or do you have the large oval ports?
The peanut ports, the intake runners look like "o" whereas the large oval ports are shaped like "0". A set of factory iron heads, casting number 049 or 781 are the best factory heads, a set of 2.19/1.88 valves and a gasket match will make em perform pretty well. The peanut ports start runnin outta air around 2500rpm. You can usually find the 049 or the 781s for around 2-300 for a set that needs reworking, which a valve job, surfacing, new guides, etc will probably run in the 2-300 range. So say 600 total for heads if you decide you wanna do it.
It'll add up quickly, heck, I originally started with a $5k budget and it turned into a massive case of the "might-as-wells"