Good morning Gas i have fitted these to my SWB
The main problem was that the base of the new seat is very narrow , and i could not find a pair of universal runners large enough that would bolt to the seat and also to the floor of the Z3 , i ended up attaching the runners to the seat base and then bolting two pieces of steel plate at 90 degrees across the runners to attach to the Z3 mounting points , hope this helps , Geoff .