When you get it back, have a freind turn the key while you connect a volt meter to the smaller wire on the solenoid. It should show Batt voltage when the key is in the crank position. If you have Batt voltage at the small wire while in crank position check for voltage at the positive cable at the starter (key off). It should be same as battery voltage, but if within a couple tenths the car should crank. So if voltage is near battery voltage at both terminals I would take the starter in to be tested. If it is not the same as battery voltage start cleaning ground connections. Very often people neglect to attach the ground cables from the cylinder heads to the firewall. I have seen cars fail to crank just because of a missing or poor ground. Make sure the engine is grounded to the chassis firewall etc. This could be done with your ohm meter one lead to the neg. battery post and the other at the engine firewall etc. (bare metal) The readings should be near 0 resistance. If no voltage at the small wire you will need to work backward testing all of the circuits involved with the ignition circuit. I had a 68 many years ago and often had to do the screwdrive trick, as the headers heated up the starter it can be done but it is a bit tricky. Good luck. I would be more than happy to walk you through send me an e-mail and I will give you my number.
tonydrcnut@sbcglobal.net