here's mine from back in the day
I ground off the black lines inside, polished it until clear again, then painted the rest of the lens to match the car, leaving a clear space for a strip of LEDs that would sweep on and off in the direction of the turn signal. The left side has the same "ceiling light lens" material you used, and the right is just clear.
LED board pic here
and an early video of the controller.
rayfinkle21's Channel - YouTube
I started drawing up plans for the LED controller in 1999, got busy, picked up again in '04/05, had a kid, played around again in '08 (date of the video) and have been kinda busy with life every since. Someday I'll finish these, and they'll be awesome. Lets just say I was less than thrilled to see that the new mustangs have this from the factory, because when it is done, now I've copied the mustang. oh well.