Thanks for the suggestions Neil.

Sure enough, region 14 is exactly the same as fw_all.bin from version 2.30 but the FAT32 file system in region 48 is missing just about everything. No idea how this could have happened. Is there any chance that region 48 is just a r/w overlay to the real file system and that my files are hiding elsewhere?

If not, I guess I need to recreate the file system without having access to the Nuvi's USB interface. Could I run webupdate.exe against a USB flash drive containing /Garmin/GarminDevice.xml, then copy the files to the mounted disk image and xrgn the image back to region 83?

Here's the details (Unix shell commands and results):

$ ls -go 14.bin fw_all.bin
-rw-r--r-- 1 52428800 Jan 1 1980 14.bin
-rw-r--r-- 1 8878336 Feb 22 21:19 fw_all.bin

$ dd count=8878336 bs=1 if=14.bin of=14.bin.first
8878336+0 records in
8878336+0 records out
8878336 bytes (8.9 MB) copied, 26.042 s, 341 kB/s

$ diff 14.bin.first fw_all.bin
$ echo $?
0

# mount -t vfat -o loop 83.bin /mnt/tmp/

$ ls -lRa
.:
total 24
drwxr-xr-x 6 root root 4096 Dec 31 1969 ./
drwxr-xr-x 11 root root 4096 Feb 22 21:38 ../
drwxr-xr-x 4 root root 4096 Feb 14 19:30 .System/
drwxr-xr-x 2 root root 4096 Feb 22 20:11 GPX/
drwxr-xr-x 2 root root 4096 Feb 22 2015 Garmin/
drwxr-xr-x 2 root root 4096 Feb 14 20:12 Poi/

./.System:
total 16
drwxr-xr-x 4 root root 4096 Feb 14 19:30 ./
drwxr-xr-x 6 root root 4096 Dec 31 1969 ../
drwxr-xr-x 4 root root 4096 Feb 14 20:11 Diag/
drwxr-xr-x 2 root root 4096 Feb 14 19:30 GPS/

[Diag(nostic) folders containing sad tales left out (can be supplied if anyone's interested).]

./.System/GPS:
total 900
drwxr-xr-x 2 root root 4096 Feb 14 19:30 ./
drwxr-xr-x 4 root root 4096 Feb 14 19:30 ../
-rwxr-xr-x 1 root root 151788 Feb 22 2015 ARC.BIN*
-rwxr-xr-x 1 root root 748032 Feb 22 2015 BEE.BIN*
-rwxr-xr-x 1 root root 7800 Feb 22 20:54 mt.nvm*

./GPX:
total 12
drwxr-xr-x 2 root root 4096 Feb 22 20:11 ./
drwxr-xr-x 6 root root 4096 Dec 31 1969 ../
-rwxr-xr-x 1 root root 1845 Feb 22 20:11 Current.gpx*

./Garmin:
total 36
drwxr-xr-x 2 root root 4096 Feb 22 2015 ./
drwxr-xr-x 6 root root 4096 Dec 31 1969 ../
-rwxr-xr-x 1 root root 24903 Feb 22 2015 GarminDevice.xml*

./Poi:
total 16
drwxr-xr-x 2 root root 4096 Feb 14 20:12 ./
drwxr-xr-x 6 root root 4096 Dec 31 1969 ../
-rwxr-xr-x 1 root root 4146 Feb 14 20:12 poi.gpi*

and that's all (no maps, voices, ..., nada).