Yes, I have. It was quite easy to do actually.
You need to find an 84 and cut the inner third lamp socket on either side.
These will replace the two wire socket next to the reverse lights.
The 84 was the only Notchback that had all three light up originally.
Wire in the park light and ground on that socket, then follow the instructions on the sequential module...
I installed them many years ago, and got tons of comments on them. You may need an electronic flasher that slows the turn signal pattern down though..
Also, there is an optional wire that can be run to the very front under the dash.
This is so that when you hit the brakes, if this wire is hooked up, your lights come on steady without cycling once.
If you do not run this, then when you hit the brakes, the lights will cycle one time, and then stay on steady.
I did not run this wire, as I felt it made the car more visible during initial braking.
Also, pick up the third brake light flasher. This pulses the light several times at high speed before coming on steady, and mounts right up by the light under the cover.
edit: The ducks are plotting mankind's downfall...
[This message has been edited by Synthesis (edited 12-01-2010).]