Dez you would use some fabricated Alum washers, I don't know who is making them now. My self I am liking the idea of using Metric Thrust bearing washers instead, 31mm ID x 18mm OD x 1mm with stackable 1mm shims washers.
With the gab being increase from OEM width of 22mm to RM bearing width 18mm, I am wondering if these would work? OEM thrust washers are 2mm wide with a 1mm instep.