Huh. I learn something new every day. I thought all Cadillacs of that era were 5x5.look into late 1970s Cadillac Seville axle shafts, and in fact the entire axle. I have no figures, and I'm way too lazy to look it up. The axle is another 8.5" ring gear, suitably used in a "compact" car having an emissions-choked (Olds) small-block, using the 5" bolt circle and rear disc brakes. Seems to me the first year of production ('75) had rear drums and 4 3/4 bolt circle, but was improved for '76--'79.
From Wikipedia: "Early Sevilles produced between April 1975 (a total of 16,355) to the close of the 1976 model year were the first Cadillacs to use the smaller GM wheel bolt pattern (5 lugs with a 4.75 in (121 mm) bolt circle;"