Chrysler's 9 1/4 is stronger and has a larger ring gear then Chevy's 12 bolt axle has. I bet if you look around you can get a 9 1/4 way cheaper then $450. I think even $450 is too high for a 12 bolt. The 12 bolt and 10 bolt GM axles have a history of the C-clips letting go. I don't know this for a fact but i've read that the 9 1/4 has the same axle shaft size as a Dana 60. As far as the 12 bolt being a bolt in, its not. Different spring pad widths and the leaf springs are wider on Chevy's and also the parking brake mechanism won't hook up.