I've done similar things with ssh pipe tunneling and dd ala:

,,, dd if=/dev/sda | ssh user@host "dd of=/some/other/file/or/disk" ,,,

Should really do it while the root is ro, but in a pinch this will mostly be ok on a quiet machine.

You might be able to run rsync afterwards to spot check if you are paranoid.

If you didn't need block level I would have suggested just using rsync or rclone.