The H&R spacers are quite good stuff. I have a set on my E30 M3, and have used then for driving around and 300+ track days.
In the meantime, I found these guys, and use their spacers on my M Coupe track car:
https://www.42draftdesigns.com/
Especially, with spacers, forget bolts. Go with studs as they make mounting a piece of cake. Bimmerworld has Italian-made studs which are great. You see the 300+ track days on my M3? Those are all on the same Bimmerworld studs. Nary a failure if you follow the installation instructions and torque your wheels properly.