Detailed instructions on adding features with application from post n1
You have lolypop files made for 35xx from his previous post:
As said before you must change HWID for your 37xx, so rename folders to 1101 instead of 1258, then extract from 37xx gupdate.gcd
( you can get it on37xx Garmin update page clicking on HTLM origin
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the boot.bin with RGNtool (see picture above) ,rename it to Ldr.bin and replace lolypop's Ldr.bin in Garmin/Updater/1101 in both folders: For backup region 140 and For write back reg 140.
At this point
1) Backup region 140:
Put the files in an empty SD, insert SD in nuvi and turn nuvi ON and wait (nuvi will turn off and on himself when all is finished)
Now you will have on SD reg_140.bin , copy it to Pc . Copy it twice(one for backup and one to use it now to enable features).
2) Delete Garmin folder from SD.
3) On Pc open Lolypop folder :3xxx series enable features application and open Mod_3xxx.exe
(you have also picture inside for tutorial) and modify and save your file 140.bin using Mod 3xxx.exe.
4) Extract on empty SD card Lolypop's For write back reg 140.rar.
5) Add your changed reg_140.bin in folder Garmin (you will have on SD now Folder Garmin and
reg_140.bin on root of SD)
6) Insert SD card in Nuvi and turn it ON and wait that nuvi turns off and turn on himself.
Edit: I see lolypop made files for 37xx, but may be you'd like to understand how he made them