I found pre-drilled holes and pattern in the masonite board on my 3dr MkI. It is visible only after you remove the black plastic foil covering it. I am not sure about the pattern diameter as I did not use these - I found them only after drilling new holes for my speakers.
I did not like the idea of fitting the speakers into the pockets (ingress of dirt etc.) and used the provision on the rear plastic shelf supports instead. These, I believe, are for 100 mm speakers. It was a solution satisfactory for radio - I have no desire of running a disco on wheels - and removed them only because I needed more room in the trunk.