The frame on a 3600 is narrower than a 3100, so could you move the shock mounts to the outside of the frame? I know that the mounts on the front are inside the frame, but don't know why. Or for that matter why the ones on a 3100 are outside the frame. The lower mount is pretty close to the tire (not that it's going to go anywhere.)
Of course, you'd have to move the lower shock mounts too.
[on edit] Just looked at your previous pics showing the frame and springs. Not much room between frame and springs for shocks.

But maybe there's enough room to squeeze the shocks in there.