[bobcowan]

Your compression isn't that high, even at sea level. If you're having problems with slow cranking, it's probably not the starter, it's somewhere else.

Consider buying an off the shelf starter from Autozone. Pick one from a 5.0 Mustang with a manual transmission. You are getting a high torque starter, in a small package. The advantage to that is that if it dies, you take it back for a new one.

That's what I'm using, and it works just fine.