Ive not seen any aftermarket double din kits for a right hand drive mk1 GS300, all of the autolead type ones have always been lft hand drive. Toyota do one for the aristo, there are some part numbers in my signature link for the "mk1 Single Din Install". I made my own bracket, but I suspect there is a Toyota item. The tricky bit is knowing what to order 'cos the parts diagrams are pants. When I did my install, I couldn't fins any adaptors, and as I had no plans to revert to factory headunit, I just cut the connectors and fitted ISO plugs to the factory harness (So I could connect the parrot handsfree kit in as well). I bypassed the amp in the boot so that I didn't need to run new wires to all the speakers.