Different upper A arms?

[GTVeloce]

I've come up with another Alfa anomoly! I was under the impression the front suspensions for the 116 and 160 series were basically the same (I'm excluding the torsion bar length and ride height). However, I bought some new upper bushes for where the A arm meets the body and have discovered all is not the same! The 116 bush is 1.5mm too large in o.d. to fit into the 160 arm. It does fit perfectly in the 116 arm. Has anyone come across this before or is this something unique to my car? i.e. warpage of some kind.
Thanks
Julian