I tried all of the above suggestions to no avail with my usb thumbstick (used rufus like others to create the cd image). Easiest way I found was to boot with both drives after installation and run:
sudo dpkg-reconfigure grub-pc
enter through the default values until you get to the listed devices and select the actual drive you want for grub to be booted from and select that. You can then boot without the thumb stick.
Grub would not let me reconfigure using:
sudo grub-install /dev/sdb
It threw errors.