Found a good deal.

Depends on the condition of the heads, and valvetrain. A used block can be had for 50 bucks at a junkyard, so anyblock that is not cracked is going to be fine for a rebuild, since it will be machined and new parts put in. I would be concerned with the cylinder heads. Make sure that you have them pressure tested to make sure there are no cracks. Give them a good port job as well when its all apart.