Starter not disengaging?

Long story sorry. Need the details. I have a 1972 Duster with a 360 LA block and a 727. I completely rewired the car using a painless universal Mopar wiring kit. As I got to a point I could ops check the engine starting system I bumped the ignition and it fired. I finished the complete car wiring and began putting the car together. I installed a brand new MSD mini starter. Went to start the car and heard grinding. Shut it off and duplicated the grinding two more times. After an inspection not turning much up I tried to start and only got a single click. Determined the new starter had a stuck solenoid now. Had another brand new MSD starter shipped and installed. Fired right up but still grinding. So I began checking wiring. I have a 00 battery wire going from the positive post on the batt to the large post of the starter. A 10 gauge wire going from the large post on the starter to the starter relay. Then a 10 gauge wire from the small post on the starter to the starter solenoid post on the relay. I have a yellow 10 gauge ignition wire straight from the steering column to the solenoid, and the neutral safety switch going to the other post on the relay. I’ve tested everything. The starter solenoid is getting 12.5v when the key is turned to run. The power goes away when the key springs back like it should. Battery power is solid. Tried two brand new batteries. The relay is getting power when the key is turned to run. When the power is off the starter gear is recessed back in the starter. Why is the starter not disengaging clean during operation? Is it a ground issue? Is it to much engagement? I know Mopar starters aren’t shimmed. I tried it with washers just to try, and it didn’t do anything. The mount seems aligned when installed. The front side of the flywheel teeth show the grinding evidence. I apologize for the length, and appreciate any guidance.