How about the shims that go under the starter, are any there. were they lost? If the gear is bottoming out on the ring gear it will take a lot more to turn that motor over. Just a thought.
John

3 90 Trooper V-6's, 5 speed, 4.3L TBI, 31" BFG AT's, Fender Flairs, Bored intake, 1.6 roller rockers, MSD Coil, Jacobs Omni ignition. Heavy duty torsion bars, Rancho 9000 Shocks CAN'T SPELL, TO OLD TO LEARN, GOD BLESS YOU IF YOU CAN.