I had these 65mm steel gantry plates you can find on Amazon. I modified the pan head mount to accomodate the use of these plates. I did have to drill the plate holes to work with the tripod screw mount screws.
The ¼-20 screws I picked have flat heads which was needed to clear the extrusion under the gantry plate.
The author remixed this model.
This remixed file allows you to use the bearings and pan platform with a common steel gantry plate(65mmx65mm).