The same firmware that we currently use on the Rostock Max v2 will work with your Rostock Max v1. You can download it here on our GitHub
You will need to make one change to the firmware for it to work on your Rostock Max v1. You will need to invert the Y axis direction in the configuration.h tab.
The setting to change in on the Configuration.h tab on line 634 and should be: #define INVERT_Y_DIR true