I'm working on redoing the interior of my '85 (wrap around dash leather seats and door panels) and was wondering if there is a subwoofer enclosure that will fit behind the seat or anywhere else in the cabin. thanks

There are a few threads on this, look at the past couple of months or so.

hey i made my own subwoofer enclosure that fits where the stock one is-under the passenger side dash under 4x10 speaker! i also made my own box out of plywood and used sylicone caulk to seal the box-i also made this box for a 8 inch subwoofer instead of the stock 6 inch subwoofer and it really sounds good! my car was not set up for this since this subwoofer option was not available in the 84 coupes but mine sounds better then stock and it is alot cheaper!!! the cost of the rockford fosgate sub was 65.00 and the plywood was nothing but scraps from the garage! hope this helps you out!!

I use a 5 1/2 Bazzoka Base Tubes behind the seats and I have a pair of them....Sounds really good...Also I have the factory Sub-woofer I just disconnect the main Sub-Woofer and connect it to my Bazookas...Now I can conrol my Bass....

In one of my Fieros, I found a 12"x12"x5" sub box and mounted it behind the passenger seat. The Fiero I just bought today has a sub box where the console storage door used to be. Pretty slick job and sounds good, visible from the outside though. I've heard of others building a sub enclosure down in the passenger side footwell.