Bonesmobile
The engine can be valuable to an Oldsmobile restorer if it is a vintage year. That is a relative term, I know, but if the engine has #5 or #6 heads it is likely early 70's. The heads are one way to date the engine, color is the other if again, if is original, Bronze is a good indicator. One caution is that every olds small block can have any olds cylinder head bolted to it if someone changed them for what ever reason. If it runs well and you don't care to use it, then 700 bucks might be a reasonable sale price if you don't want that awesome Olds torque :lol:
If you give me more info regarding color of the block and the large # off the head near the the ends facing up, that is where the #'s are. They will be like 7A or 6 and so on. The lower the # the older the head generally.
I know that you are on E bay looking at an ad, but if you saw the casting # on the heads between the center head bolts below the valve cover the best #'s are 147 or 742 made between 68 - 70 and the best stock W31 pieces are # 405585.
Bruce