Utilizing LiteSpeeds LSUP script, you can upgrade/change to a specific version of LiteSpeed with the following command, where the -v flag is used to specify the version number. In this case, the upgrade would be to version 6.0.
/usr/local/lsws/admin/misc/lsup.sh -v 6.0
LiteSpeed also created the following blog post which goes into more detail of how to use the LSUP script: Auto Update With the LSUP Command.
And to see what versions are available, refer to the LiteSpeed Web Server Changelog.