Looks to be a '72 or '73? If he believes craigslist prices, he could start at 8K or 9K and see what happens.
Looks like an older 350 with maybe no provisions for a power steering pump? Looks like it currently has manual steering? Did the conversion use AA components? What does the wiring look like? Did he tie into the factory harness or does it have a different harness?
Depending on all of this, I would think it would lay in the 5K to 6K range...