What I have done is to obtain Plaque mounts from a trophy store and mount GTs to them. Below is a 1/43 Minichamps model (picture 1) which is mounted to it's own base by a small metric screw from the bottom (picture 2). I then obtain a longer screw from a hardware store and, after drilling a hole in the plaque, assemble the pieces together using the longer screw (picture 3).
The model can then be displayed on a flat surface with a large wood base, or mounted on the wall either vertically or horizontally.