Sorry about that. CPP's online catalog is a bit difficult to navigate. You have to search for Impala
and still everything from 1955 to 1967 is listed together.
Here are some links to '58 - '64 Chevy applications:
CPP50003 Power Steering Box
#5864PSKS Complete Power Steering Kit
(I'm not a big fan of the 605 steering boxes)
#1140670010 IDIDIT Steering columns
Maybe just a rebuild of the stock components would bring her up to snuff?
Hope this helps,