I like Maverick75`s Firebird Spoiler - still has a vintage look - sorta like a boss Mustang. I ran one of these on a Comet GT and the fit is very good and it also matches to the body lines. Maybe someone has a rear view Photo of this setup that shows it better.
I think leaving the third brake light would be a good idea. I have a 90 Z 28 spoiler I'm thinking about using on mine, it will have to be lengthened a bit to fit the trunk lid, and if I use it I plan on hooking up the brake light. Might keep some idiot from rear ending you!
If some idiot misses my 69 Cougar tail lights then they need a cane and a seeing eye dog!! I don't think that third brake light will help. I did think about putting my back-up lights in there though.
youd be surprised, i was rear ended in the wifeys cougar with the brake lights shining in his eyes as i watched him creep into me. luckily it was minor, rubber mallot stuff. need spikes that stick out when you hit the brakes. ive also had people run into my jetski jet and outdrive on a boat, they never learn.