Thanks for the compliments guys. It took me damn near 5 hours to make that thing. I do not think I would ever do it again. It is not that hard to do if you have any experience with bondo and fibreglass. I will try to answer the questions asked above...

It is a center channel speaker.
It is a tweeter in the A-pillar.
Yes, it is very visible. I can not see the 0 very well, but my oil pressure better not ever be on 0 or there is a problem.
The only materials I used were 1/4" MDF for the base, bondo, 2 fibreglass strips of cloth, and more bondo and time. Lots of sanding.

If you have anymore questions let me know.

Oh and that gauge is one of the bigger gauges. Not the 2 1/4, I think the 2 3/8 or something like that. So in theory the holder for a 2 1/4 gauge would be easier. Just thought you would like to know.