In the Xeoncross fork (https://github.com/Xeoncross/lowendscript/blob/master/setup-debian.sh),
where it is creating the /etc/xinetd.d/dropbear file, you can add these 2 lines to set a different port for ssh than 22:

port = $1
type = unlisted

along with an earlier check for a port passed as an argument:

    if [ -z "$1" ]
    then
        die "Usage: `basename $0` optimize <ssh-port-#>"
    fi

and pass that argument from the optimize function to the install_dropbear function:

optimize)
    install_dropbear $2

Another way to change the port apparently is to edit the /etc/default/dropbear file.

But I noticed the Keith2 port (https://github.com/Keith2/lowendscript/blob/master/setup-debian.sh )
uses the same method, too (setting port=value and also type=unlisted).