E30 use different strut inserts depending on engine size. Here is a radical suggestion - take your strut insert out and measure it. While it is out go to the local suspension shop and buy the replacement of your choice - performance or standard. This has worked for me in the past.....
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 White and 1 Light Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i