Find a GOOD local shop that rebuilds starters, and take your starter to them. I have a rather high compression (9.8:1) 469" motor, with headers and a trunk mounted battery - all things which typically cause starting problems. I had a local shop rebuild my GM/Delco hi-torque starter years ago, and I have NO problems, even when the motor is hot.
Lee
'67 Coupe, 455, pump gas, 11.46 @ 115.4, in Feb '05 HPP Shootout article