Bucs012,I have the battery in the 34 in the exact spot as yours.A slight angle is ok ,as the batt is not always level as you drive up and down hills on the road.You can measure the difference front to back of the batt and fabricate a frame to make it level,then mount your box on top of the frame.The void between the seats and trunk is really a good spot to put a lot of add on things like batt ,fuse panel,stereo antenna,etc.JMO

My panel is velcro on top and mounting studs w/brackets from the steel frame on the bottom (See Gallery)to carry the weight of the panel.