I don't know exactly but you can try.
For 3790LMT ::
I guess your device has 1101(HWID)
Please comfirm this hwid number by pressing battery icon for a while till you get in Inventory page.
And check your hwid out.
For hwid 1101 ::
You can try to use original US boot.bin saved from original US gupdate.gcd swv 2.50 to swv 4.10
Then combine 3 parts ::
US boot.bin (HWID1101) + Sg/My2.30 resources.bin + Sg/My2.30 fw_all.bin (replace hwid 1288 to 1101 - same as boot.bin) --> out.rgn
Please prepare an original rgn file to come back US.
Using original US gupdate.gcd save to .rgn file.
If you get rebooting loop so just flash your nuvi with this original rgn file.