Does anyone know what this might be???

I am building my 70 Dart with 383, 727, 8 3/4, and I'm at the point where exhaust is all on and I drove it around some today.

The issue is, I am getting a bit of starter noise just every once in a long while... I have no idea why??? Just driving around, and I'll get a bit of noise n then nothing...

I tried to sort of shim the starter (spacer) but no...

Is there some way maybe I need to tighten the torque strap a bit n the motor is moving n causing this? I am just guessing, NO IDEA...
Check to see if the starter is hitting the block. Some block castings have extra material in the pocket where the starter fits causing the starter to mount a little crooked. You should be able to slip a piece of paper all the way through that area between the starter and the block.