Having never seen the car, it looks like there might be a cover in the same style as the panel just in front of the subs. There looks to be clips or something up by the window and small holes between the panel and the cloth of the enclosure for tabs to go behind the panel infront of the subs.

The lego bricks (assuming you mean the grey boxes with knobs at the very rear) looks to be 30 band equalizers.

/Michael