Prices are all over the place for the high performance engines for Camaros or anything else. Go to eBay, auto parts, type in 3956618 in the search block and you'll get a chance to buy anything from genuine (?) DZ's to 350/255 HP blocks to clones. At anywhere from a 70% price reduction from this ad, or 90% for a bare 6618 block. To the owner of the car that this (hopefully) original DZ block came out of, it would have an appropriate value, probably still not this much. Shameless speculation is you want my opinion -
Regards,
Steve