I have never liked the look of the box hanging under the rear spoiler on the 87 Supra turbo.  With my 87 Supra parts car I have an interior brake light and I plan to install it and remove the exterior one.

The connector for the outside brake light in under the hatch cover panel.  As it turns out, it is the same connector for the interior one.  Also, all the mounting holes are there for the interior brake light.  Since almost everything is black and interchangeable, the only things I had to do was paint the light cover gray, cut the hatch cover panel like the one from my n/a, and plug the holes in the spoiler with gray RTV. 

I put a piece of paper on the n/a hatch cover and drew a line along the indent.  Then I transferred this to my turbo one and cut it out using the dremel. 

I also had to repair one of the hatch cover panel tabs using 60 second epoxy.  It says 60 seconds, and it means 60 seconds, so work quick.

1- Having to cut the panel is all that makes this hard.  Once its cut, there is no easy way back.  Try to find a donor car with the same interior color and you can swap the light and the hatch cover, no cutting and no painting.

1- I have been rear ended in this car, but that was before this mod.  My only concern is that this interior brake light is hard to see by other drivers during the day since it's behind the wing.  Truthfully, I wouldn't really care whether I had one or not if it weren't for the law.

The payoff is purely subjective as not all will dislike the box brake light like I did.  I think that this was a great, simple, and inexpensive mod.  I really would like an LED module instead.

In my year of car the 3rb brake light is this square box that hangs under the rear wing.  It doesn't even try to give the appearance of stream lining.  In 89 (I think) the light was angled a little bit.

I like the look of not having the light on the exterior of the car.  Again it's an esthetic thing.