Now that the heads are off you saw anything that was in there and then some...you wont know which valves were open but you can probably read the rust traces on the cylinder walls. Now you can tap the piston crowns down alternately with a hammer handle or wooden dowel and a mallet to loosen the pistons, ( I said "tap" not drive)! Keep 'em wet with the rust penetrant or diesel fuel and keep working the crank back and forth until free. After you drop the pan and the rod/pistons are removed you can run a cylinder hone in the bores to determine the extent of the cylinder pitting. Don't try to bore them out just a light honing will do! HTH