Dennis, you’re definitely going down “the road less traveled”. That road can be very lonely at times.
That said, you should be able to take the instructions for dual end-endstops on the MPCNC and apply the instructions for the X axis on the MPCNC to the Z axis on the LR2. You will definitely have to monkey with the firmware to get it all working. If you don’t have your heart set on using Marlin, there is a port of GRBL to the Rambo board made by @johnboiles. That thread is here. There is a guy on that thread who used the firmware for his LR2.
Happy Hacking! I’m going to be going down the same road over the next few weeks (though I’m using a RAMPS board; not a Rambo).