Is it possible in steam to revert to pre-1.90 versions, or am I stuck?

I’d like to play the game with the mod collection that I had accumulated before the 1.9 patch came. Is it possible?

I know that steam has a mechanism for allowing users to load different versions of games, but it doesn’t look like that dropdown is populated for K:CD.

it is populated: just did it myself. just google for download_depot and how you can download older versions.