The BOSE was not an option for the '96 SS, or Caprice for that matter. The only time a BOSE unit was available was in '91 (maybe '92 also). It was based upon the previous (pre-'94) generation radios.
The '96 Corvette did have the BOSE system, but I believe it's more involved than just swapping head units. I don't even want to know what Corvette audio parts cost.