I have a method to create a single track with lines 1km apart and aligned it with UTM coordinates. Seems to work well for Basecamp/Google maps and certainly makes them more readable. I can pump these out en mass to cover Oz (at least the important bits) if it's useful. They seem fairly accurate which can be improved with more intermediate points along the lines since it's not a straight line from EW/NS. At the moment 12-15km spacing gives reasonably accurate results but I may reduce that to 10km.
The 50 x 50 km grid is one track consisting of 407 track points in total with a waypoint on each corner for reference. Only 28kB as a GPX file. There's no numbers on the grid.
Here's an example to view, download and plug into Basecamp.
UTM Grid Kosciuszko - https://www.google.com/maps/d/viewer?mi ... sp=sharing
How it looks in Basecamp...
In Google Maps...
