69 340 problems

Are you still running your Corvette coil? When did you switch over to it? You may want to switch back to your Mopar coil. It is made to run on 6v unlike the 12v Corvette coil. As long as we're grasping at straws, it's worth a shot.
No, Grump. I put that Delco coil on it just to see if that was the trouble. Once I knew that wasn't the trouble, I removed it and reconnected my Mopar coil.
You say the car tries to start when you let off of the key and put it in the run mode? I had this problem with my car. I had something wrong in my switch that wasn't sending power to anything but the starter in the start mode. Put the key in the run mode then jump your selonoid. It worked on mine hope this helps. If it works their is something wrong with your switch, Mine had a pushbutton ignition on it now so its fixed. Probably won't work but its an easy try. Good luck Rick
I just ran out to the garage and tried it your way Rick. Turned the key to run, and jumped the starter relay with a screwdriver. No start.

George