Try this link to Rockauto.com they list all the part numbers.
http://www.rockauto.com/catalog/x,carcode,1325933,parttype,1672,a,www.google.com%2BSearch%2Bfor%2B1958%2BCHEVROLET
I just converted my 58 3200 about 2 weeks ago - just got it back on the road yesterday. It is super easy to do. Only took a few minutes each side.
