George, I'm assuming this was a canadian skylark, the rear was a factory item with the Buick yoke. I busted my 10 bolt in 1990, and just dropped the 12 bolt in its place. I am now starting to repair all of the abuse I put my 71 GS through as a teenager. So I guess I can assume this is the chevy rear and the size is 8 7/8. Thanks Tim
