As your existing is damaged take off the head and look. Compare and then decide which to use. If you mix and match make sure the combustion chambers are the same volume. A good head shop should know how to check this.
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