Get a spare decklid. They go for about fifty bucks, and you can get it painted at the same time as the tail, so you're not going to have to spend too much, and you never have to worry about being able to go back to stock.
For my car, I've had three painted. There's stock (in the unlikely event I decided to sell it, this one would go on), and then the ducktail, and now (currently being wired) the 964 with retractable tail.
First report on the 964 lid on the early 911 body? It really looks great. I know it will irritate the purists, but these cars wear the changes real well.
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Jack Olsen
1973 911 T (3.6) sunroof coupe