another update:
Finally finished the install this weekend, was tweaking a few things and fitting a cold cathode to light up the sub which matches the dash conversion. This is on a switch on the panel where the traction is. The box was built out of fibreglass and sound deadening material, then we fitted an MDF top so we could mount the sub.
Ive gone with this dual voice coil Hertz 10" sub on the recommendation of a very good audio place and im very happy with it, the sound is amazing. Ive wired it up to drop the amp to 2 ohm so its nice and punchy.
The amp is a 4 x 100 clarion one which ive powdercoated to follow the theme of the car, ive sat this on on MDF base and screwed it in with security screws then cut out the top piece so it drops over it and hides all the wires.
You'll also notice the new 4 point harnesses ive fitted in place of the old 3 points. I prefer the look of them on the harness bar.
All in all a very productive weekend. More to follow shortly..