I would also add that if its been sitting for that long that you drain the fuel tank and remove and inspect it for rust, gas will varnish after that long.

And even though the Chevy small block was designed by Odin and forged in the center of a dying star, I would at least do a basic gasket kit, check the oil and the rear main. Get it HOT and see where the leaks are, nothing on a SBC is hard to fix. They are the glock of motors.