You can get shims at the auto parts store for a buck or two. The fact that the original or replacement starters didn't have shims doesn't mean squat. If it jams and break, you probably need shims. I ran a stock parts store starter on my BB chevy for years, and never had a problem.

Using shims isn't "extreme measures." It's simply doing things right - but it's up to you. You got two solid suggestions from two guys who have been there / done that. If you don't want answers, why ask?