Hi. It's a common aftermarket billet spacer that is drilled to an 8 x 6.5 lug pattern and has lug bolts in the same pattern. Available virtually anywhere. Bolt it on your hub. Then bolt the rotor on to it. Yes, 1/4" mild steel plate.

"If it sounds cool, then it is cool"-Billy Gibbons
I gots a 1950AD 250L6/700R4 and a '52 1 ton Panel

http://i1206.photobucket.com/albums/bb460/gibsonflatpicker/ChevyPIRI.jpg ====The truck
http://i1206.photobucket.com/albums/bb460/gibsonflatpicker/woodyOct10.jpg =====The car
http://i1206.photobucket.com/albums/bb460/gibsonflatpicker/bikeaug09.jpg ====The bike
http://i1206.photobucket.com/albums/bb460/gibsonflatpicker/Panel_zpsszb2b6bo.jpg ======52 1 ton panel (the newest member)