Your engine will loosen up over time. How many mi do you have on the new engine?
If your header pipe come in contact with the starter housing then dipple the pipe so the pipe does not touch the starter.

I don’t where you can get a shield I cannot see how the shield can do anything for situations where starter is in contact with pipe.

BTW, how is your alternator? Have you had a rebuilt?
If you get the right service guy it’s very inexpensive to rebuild your Alternator

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