All right, i'll made it for you but i do need for you to understand and acknowledge that flashing any modified fw is not without risk even when using original boot.bin and retaining HWID.
With the 41, yes that's what i said: to extract it to the card i.e. 'extract' as in 'decompress' or 'unrar'. Please make sure you have the 41.bin before you go any further.
So, here's the modded rgn file and some other TWN specific files and US voices. The rgn's been changed to accept the US/EU fw voices Jack, Emily, Daniel, Karen, Lee, Sangeeta, Javier [ES]. Paulina [ES] and American English & British English [both non-TTS]. Jill and Mei-Ling [Chinese] are original voices in TWN fw so are unchanged. Some of the vpm files are old ones, i've used them to get the job done but you can connect to WebUpdater and dl any updated voices offerred if you want. Be aware that some pronunciation may be a little quaint when using these EN voices with the TWN fw.
Brief How To: Extract the file TWN_Files_Flash.rar somewhere convenient on your PC. Connect in MSM. Copy the two folders named 'US_files' [it's empty] and 'TWN_Files' to your 765's Garmin folder. Move your existing folders ExtData, Help, RemoteSW, Text and Voice to the folder US_Files. Open the folder TWN_Files and move all its sub-folders to the Garmin folder. Safely disconnect from PC. Open the folder named Updater on your PC and drag 087001000330.rgn onto Updater.exe and leave it open and visible on your desktop with the 'USB Device' radio button enabled. Put the unit into preboot and immediately press 'OK' when you see it's details appear. Keep holding the screen at least until you see 'Loader' appear on the screen. Hopefully, you'll enjoy your new toy and won't brick it. Good luck, here'e the rar file: