Download and extract the Map folder.
Copy the Map folder on an empty micro-sdCard (formatted FAT32) in root folder (sdCard G:\Map\), use a sdCard adapter to plug it in your pc and open Basecamp.
When you receive your Montana or Zumo, insert the card in the slot in the device.
No need to change the file names of the two maps in the Map folder.

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Spoiler: Legend for custom TYPs

1. AnaDigit
-- Green___Major Highway
-- Light Green___Highway
-- Red___National Road
-- Orange (wide line)___Major Road
-- Orange (narrow line)___Minor Road
-- White (red borders)___City Road
-- Yellow___Major Dirt Road
-- Lght Yellow___Minor Dirt Road
-- White (black borders)___4x4 Dirt Road
-- Black+Yellow___Trail

2. Topodrive
-- Green___Highway
-- Red___National Road
-- Orange___Major Road
-- Yellow___Minor Road
-- White___City Road
-- Brown___Dirt Road
-- Red+transparent___Trail (the Trail line is very wide because Trails in this map are drawn "under" some roads, so to be able to see both Trail and Road in most zoom levels, Trail line must be wider than the Road line)