I am kinda surprised he wouldn't just state a price. Making a trade is more tricky IMO. Hopefully the 5k he has in it, would have been similar to what you would have done with it. Keep the dialog open. if there are other parts he is looking for, try locating them on ebay, and equating a dollar amount for them. You pay him the money and he can make the purchases, and get what he wants. Or there are many DZ blocks on ebay, find a date that works for him and he can go purchase a date correct block. Just a suggestion to make things go smoother.
This way if you pay him and there is an issue with what he purchases, it is between him and the seller. While just your block will be between him and you.
(Speaking of Indiana, just make sure you never deal with a seller out of Angola Indiana..."re-stamp city " with that guy