Hi Vick
The main modification needed to the Sierra upright is to ream out the lower ball joint mounting lug in order to accept the Austin Maxi ball joint.
The original Sierra lower ball joint has a smaller taper & can't be used on the Roadster.
The musroom adapter is used to replace the Mcpherson strut used on the Sierra hub assembly.
Simply fit the mushroom adapter into the hole where the strut would have been, this will allow the fixing of the top wishbone via the Transit drag link.
Please note, the mushroom adapter will need a secondary fixing in adition to the original pinch bolt ( Required for IVA )
The part numbers for the joints are floating about on the forum somewhere as is a drawing of the mushroom adapter needed.
Being as you are buying your wishbones from 3GE you may as well get your Mushrooms & joints at the same time
