Jim,
I am the guy who can build boxes for your Supra. Sorry for the long delay in responding.
I am able to build a box that holds most 10's and maintains all spare tire tools, tire and retains targa storage.
That box is $350
I can also build one for 2-8" subs that would be the same price.
I haven't built a box that would use 2-10's, keep the spare, tools and targa storage. That would be next to impossible in the rear area of the car.
I play around with the idea of losing the foam to the right and the left of the tire and maybe constructing a box there but I am not able to get the depth needed to still maintain targa storage.
I can build a completely stealth box that houses 3-8's, 2-10's, 3-10's or 2-12's (using the correct subs however) These boxes go down into the spare tire location and would have to be built of fiberglass. They are somewhat time consuming to build and would run $700 or so..depending on a few more factors.
I can and have shipped boxes to Supra owners all over the country. I have references and have done probablly more stereo systems in MKIV's than anyone in the country.
Might be OK to just call me sometime if anyone is interested.
Thomas Kenyon
Custom Sounds
San Antonio, Texas
210-340-4000