Why not just use the ones designed for the job?
http://www.sbig.com/sbwhtmls/online.htm
10064 Camera Lens Adapter $119 35mm Camera lens adapter (Specify Canon FD, Nikon) for ST-8300 cameras with filter wheel.
CLA7-8300 Camera Lens Adapter $165 35mm Camera lens adapter (Specify Canon FD, Nikon) for ST-8300 cameras without filter wheel.