Back in UE4 beta days, i created a 3dsmax script to export some of my old meshes created for UDK to UE4. Since there was a lot of meshes i decided to write a Maxscript that will process all the FBX meshes from a given folder and export them to another folder as 2013 FBX so you can add them to UE4 without any compatibility errors. Later i also added the ability to export scene meshes too.
I thought its better to share it here so 3dsmax guys can make use of this. 
How to use (If you want to convert old meshes from folder):
1: Navigate to your folder path that contains old FBX meshes (FBX Files Path field)
2: Choose the files from the list
3: Choose options
4: Select a location where you want to save new FBX’s
5: Click Export Files. Grab a cup of coffee and relax.
How to use (If you want to convert scene meshes):
1: Enable Process Scene Files Only
2: Choose options
3: Select a location where you want to save new FBX’s
4: Click Export Files. Grab a cup of coffee and relax.
Here is the UI:
Download: https://db.tt/DX2k3uuw
How to run:
1: Open 3dsmax
2: On Menubar, click on MAXScript and select Run Script…
3: Select this script and open. You should now see the UI.
