GermanLook Forums - double wishbone ball joints

I know there are a few here making a bolt on setup for the bug, a few posts down. anyway I got a question I was hoping you guys can help me out with.

Are ball joints really that different? they rotate some at slightly small/larger angles, have different tapers at the threads and so on. But how likely could I find a replacement joint that wasn't meant for a particular model?

I like the miata suspension, and instead of re-inventing or even starting from stratch (suspensions aren't easy:) ) I figured a could copy another manufacturers hard work. Miata's have really nice tunable suspensions, plus the side of the car is similuar to the bug. The big problem I have is that the miata's upper arm and ball joint are one piece, need one, replace both. So figured I could find a ball joint the would fit the miata spindle and I can fix it to the custom arm which ever way I want. What do you think?

thanks
Rip