Import terrain modeled in 3ds Max?

Im hoping someone can point me in the direction of a tutorial or help explain the workflow for creating a heightmap in 3ds max then exporting to UE.
This is the only thing I have found that explains it in detail but It is now out of date and much of his workflow is not applicable to recent editions of 3ds max
I have been trying to figure out the new work around by adding a gradient and then unwrapping but I cant seem to get it to work. Im too new to the software to really know where Im going.

Thanks for reading Short 33sec video of how to apply a shader then capture a render of the grayscale, sorry i use maya not max hope this helps.