I have patched the source of kdeutils-4.6.5 since there are problems on KCalc (see this link and this link). You can download the slackbuild script, patches, and the source of kdeutils-4.6.5 from this link. Before compiling yourself, make sure you have upgraded your KDE to KDE-4.6.5 using Eric's packages. Next, uncompress kdeutils-4.6.5_SlackBuild.tar.gz and run the KDE.SlackBuild as root. This slackbuild script will compile kdeutils-4.6.5 then upgrade your previous one.
For Slackware64 users, you don't need to compile; just download the binary package from this link, then do upgradepkg.