My donor car for my 16i 4x4 is an xr4x4. As I've now found out, the xr4x4 has a wider track on the front end. I know the cossie has a lesser track so can I swap the hubs and shafts from a cossie onto the xr4x4 to reduce it? Are the bottom arms and anti roll bars the same? I don't want the front wheels sticking out more than they have to

 

Yes.
Cossie shafts are shorter and the hub has a smaller offset. They are about 15mm narrower than the xr. Strut hole and TCA are the same as the xr.
Roll bar is thicker on the Cossie but will fit in place of the xr one.