Correct way to install a starter???

[n737nc]

I broke my starter(long story). And, I am going to install a new one tomorrow night. This is a 1972 with a 350 motor.

How do you know the correct amount of shims to install?

I have installed a few starters over the years, but I just reused the original shim that were there with the previous starter.

The start that has been on this motor was making some serious racket when it was engaging. So I figured that it was not shimed correctly.

So, when I install the new one, how will I know it is correct?

Thanks,
Nick