Hi Buick Bozo Check out Dans thread below. http://www.v8buick.com/index.php?threads/updating-suspension-in-a-57-buick.242437/ He put a Flat Out Engineering C4 Corvette front crossmember for 36-54 Chev pickup 29-1/2" wide in his 57. Others have also used XJ6 Jag front and rear with good results.