[Big Kev-O]

After killing about four autozone starters in a period of two month, which they happily exchanged to my surprise, I finally discovered many SBCs needs to be aligned with shims. I found instructions on this site similar to the method in the youtube picture you posted. I use a medium paper clip inserted between the crest of the starter drive tooth and the valley of the fly wheel teeth.

Sounded much better for about a month until the grinding returned. I was using grade 8 bolts thinking they were the strongest and best option. Once again after searching this site I found out that GM starter bolts had some sort of knurling that aids with and helps keep proper alignment. Five years later and it still cranks smooth as butter. I have the part number at home, will add it later.