Update, thanks to @GarminNuvi and @theob, I was able to get this to work. I did not have to use MapSource or BaseCamp or any other software.
1) I downloaded the Image files (.img), SQLite files, SID files, and JCV files that @theob posted on page 1 of this thread.
2) I then followed @GarminNuvi's instructions to Patch/Unlock my Drive 60 unit, based on the instructions in the thread linked below (I had some trial-and-error here, and posted my notes in the thread). Note that I followed this process with a different, freshly-formatted MicroSD card:
software/universal-firmware-patcher-for-protected-garmin-devices-t17987-1620.html3) Once the Drive 60 was updated, I then took the 4 types of files from Step #1 and placed them on the MicroSD card in the hierarchy depicted in the post immediately prior to this one. Note that I did not have as many files as depicted in the screenshot. This was okay. I also didn't have a "System Volume Information" folder. This was okay too.
Note: Pay attention to how the folders are nested - I originally had "Map" inside "Garmin", but then reviewed the hierarchy again and realized it had to be pulled out and be directly on the root of the MicroSD card (i.e. per the typical Garmin SD card convention).
4) When I inserted the MicroSD card back into the Drive 60 GPS, I believe I got a message saying that the maps have been updated. I then checked the MyMaps under Settings, and it shows an entry for ALL US, as well as a second entry for "ALL Canada and Mexico".
5) I was able to successfully look up and start navigation to some sample locations in Canada.
I think I am all set!
After struggling to get the "All North America" maps from my DriveSmart 61 copied to my Drive 60 earlier this week, I was happy to get these maps working using the method above.