In addition to Curtis' suggestions, it might be a good idea to pull the valve covers and check that all the valves are free to stroke fully up and down. This can be done at the same time as you manually jack the engine over.
As you roll the crankshaft (with the valve covers off) watch as the rockers push down on each valve stem and the valve opens. Then, as the associated pushrods drop away, make sure that the valve stem rises and pushes the rocker back up.
If you find any sticky valves, you can generally free them up by spraying Pblaster on the stems and bouncing the stems/springs up and down repeatedly.
One other thing to check - and this is not a joke - is that your exhaust system has not been infested by mice. This is a very real problem with vehicles that have sat for long periods of time. Mice, for some reason, seem to consider exhaust systems to be prime real estate.
They crawl up into the tail pipes and make their nests in the muffler. As the years go by, the stuff they use to make the nests gets tightly packed in the internal passages. In some cases it can completely block off the flow of exhaust gases.
Depending on the degree of blockage, this reduced flow will cause the engine to run poorly or prevent it from running at all.
