3 years ago I was given a 250 that had been rebuilt (stock specs) in the 80's and then sat in plastic all those years. I spent over $3k for a complete build with a bunch of 12bolt.com parts: Thrifty cam, 1.84/1.6 valves, cast valve covers, intake lumps, roller rockers.
If you can do a complete rebuild for $1500 please let me know your magic because I want to build another one for my wife's Camaro.