Create collision node based on orange bounding box?

I'm going to be importing quite a few purchased 3d models and they will need a collision box assigned to them. It would be great if i could do it in gdscript rather than manually. The orange bounding box looks perfect, using code can I do something like get the largest dimensions of the model and create a collision box based on that? i think basically this is what the orange box is, in terms of size.