Take him a 12-pack or whatever his favorite beverage and bring your own tools and engine stand. Offer him $100 to let you drop the pan and pull the top end. Take lots of pics. Particularly numbers on the block, heads, intake and crank. There are plenty of folks here that can help you once you have that basic information.
Anyone else considering buying it will want to do the same, so you're really helping him out by taking it apart, unless he knows more than he's telling you.
A pretty big chance to take without doing the homework. May as well go to Vegas and put the $6.500 all on red.
Good luck.