If you look at the diagrams in the FSM for the 300D N/A and the 300D Turbo you can see the difference in vibration dampers. The turbo damper is flat, the N/A is deeper.

The balancing disc is also different.

N/A indeed uses M8 x 45
Turbo uses M8 x 30

There should be no difference between US or Euro engine, there is a difference between turbo and N/A.

The damper on the right does indeed look like a N/A.

Thanks Grovert. My FSM is a North American edition dated 1991. I wasn"t able to find a comparison in mine.