Since the lifters are out, if you have a spare cam laying around, set it in the journals. If it rocks side to side, then the head is warped (or was warped at one time). You can also just look at the bearing caps. If there is excessive wear in either the #1 or #5, then the head is warped (or was warped at one time). Finally, you can check the deck for warpage with a straight edge or feeler gauge. This type of information should help you assuage some fears, and sell it faster.
Having said that, it looks like a clean head with no cracks between the valves. May have had an easy life.