lolwut?
is it like...the whole thing, or just a block, or...?
unless he has documentation that the engine has been checked by a shop, its a big "helllllll no" in my eyes. could have been overheated, the head or deck could be out of spec, cylinder walls could be out-of-round (it happens), head could have eaten a valve, etc.
unless you have an extra $125 you wouldn't mind going to waste if it does turn out to be junk...the dude could have $50 of scrap metal he's trying to turn into $100-125...