Had the same frustrating problem with my 68. Everything tested good...still wouldn't start. Had the trans rebuilt two weeks earlier and the shop set the linkage between the gear shifter and the trans improperly, so when the car was in park it had a bad contact. When I turn the key, I had to at the same time nudge the gear shifter forward a quarter inch and she fired right up. Just some info I learned the hard($) way (new starter, new solenoid, new stater cable ) Price of an education, call it. Good luck.