Gents,

                 Due to my grief in having brand new reduction alloy pulleys not driving on a new fan belt, I located the manufacturer in China, and at much reduced prices.  Just go into Ebay under "Underspeed  pulley set for RX8".  However be prepared to either lathe off (or file)  the apexs of the pulley grooves as they are too high and the belt cannot bed into the wedges of the pulley for a positive drive.  Stock supplied,  they attempt to drive on the apex only and will not drive at all.  Reduction sizes are Eshaft and water pump  4 inches and alt is over 3 inches (80mm)  The advice I received is that for high speed applications the water pump can be as low as 3/4 the e shaft speed. That means you can go as low as a water pump pulley of 4 1/2 inches or 110 mm up to 115 mm.

As I said these are cheap compared to local supply which come from China in the first place.  Neil.