I guess it would start with why it was torn apart in the first place - what was wrong. Then it depends how it was stored (high humidity = rusted steel sleeves, races, etc.)
Heads, jugs, rocker boxes, cams, lifters, lifter blocks, oil pumps - you see a lot of them for sale on Ebay. You also see some trannies & primaries. One of the big things to look at is the condition of the cases, including the races which are pressed into the case (tranny, crank). These aren't cheap and are not always easy to replace.
bottom price = how badly he wants it out the door
top price = how badly you want it
hope this helps
When workin' on your ride the first tool out of the box should be the manual