Sorry for the crappy photo, my phone was almost dead.
About 3 1/4" x 1 1/4" X 1 1/4".
I use a Chrysler pack-o-cigarettes style regulator. The three leads at the bottom are coming off the stator, the output of which is controlled by the separate regulator. The negative lead goes straight to the battery. The positive lead is going to the main lug on the top of the starter solenoid through an inline fuse. The red crimped wire attached to the ground lug is a separate ground lead to the regulator, since it is attached to the side of the battery box which is not grounded.
There is ample clearance to the bottom of my cafe style seat pan, I don't think it is an issue for any others either.