The radio and the 4th speaker will be able to install in the open void in front of the steering wheel storage compartment.
Its the other 3 speaker holes I'm unsure about. I don't want to drill the holes and find out it's not possible. I'm hoping somebody else has already experimented with this and could help shed some light on it for me.
The gas tank is under the rear seat, there may be enough room there but I'm really not sure, would be bad to find out you punctured your fuel tank the hard way.