Performance world rockers

Agreed. Honestly, even if you did the math, and then drew up the parts yourself, you'd probably spend what Mike charges, or more, to have a job shop whip you out a set of the shims. It's not cheap, but it is a bargain.
I have the equipment and the skill (theoretically) to make them, and I still don't want any part of it. I am pretty big on doing stuff myself but I'm not retired yet and certain things are better paid for than me hacking away at them. I always gave my Dad grief for hiring stuff done that we used to do ourselves after I left home, but now I understand.