You have reached my Fish Tank LED Turn Signal Conversion page. Short and to the point page. Enjoy!
An image of the "tank" from the side, exposing the LED's. Installed, you cannot really tell that there are LED's in there, as they are reflect some light.
This is the first image I took of the assembly when lit. The image was taken with flash and very bright garage lights on (4x27W fluorescent). The battery was at a low 11.66V, almost 2.5V below full charging voltage. The LED's will be brighter in the car, and even more so with a voltage regulator installed. Not having a voltage regulator set up yet, I biased them at only 85% average lum intensity to protect from voltage spikes
I took this image with no flash and the garage lights on only. Low exposure, set for daytime images.
A close-up low exposure shot.
Another low exposure shot.
And yet another to reveal the LED's.
Here's a shot of the assembly illuminating the wall, 8 feet away from the LED's. I used a night exposure, so the brightness is not correct. The wall was about half as bright as seen in the image. In person it seemed very bright for a turn signal/marker lamp assembly. 
And one last night exposure image. The exposure I used is about one half second long. In my opinion, these lamps are very bright, and will do great as turn signals. I'm 'technically' putting out more lumens than the round DOT lamps seen on trucks (I wanted to leave some room for error). I was very impressed with the lighting after I saw the tank lit up. The fluted lens of the fishtank helps the LED's achieve good off-axis lighting, quite a bit better than the DOT truck lamps. More specs follow this image.
Specs:
LED Cost: $0.39ea - $12.48 per side for the LED's
Resistor cost - $.07 - $0.56 per side
Diode - $0.33
Voltage regulator will cost about a dollar each.
LED Luminous Intensity: 4500mcd
LED Viewing angle: 23º
