CJP1-
McGowan's barrel web site:
http://mcgowenbarrel.com/.
On the home page is a link to Savage pre-fits, which include a 450B barrel. Have a look. Unfortunately for your specs, it's chrome-moly, not SS.
My smith is a pretty picky sort, but has been impressed with the McGowen barrels he's installed recently. I've been pleased with the one I had installed on my Model 70 in 2011.
--Bob