Obviously, the answer is no, if that is the way your car came from the factory. However, questions about compatibility start to pop up when taking a shelf from one car and a top from another, or buying a glass window top for a 3 bow frame. What do we need to be aware of when deviating from the factory setup?
In an earlier thread there was some discussion about putting an early rear speaker shelf (for this purpose early is 98-02) into an 03-04 and concern that the top would not fully open. That thread also lead to some discussion about the opposite (putting an 03-04 top on an 98-02 that already had a rear shelf.)
There seemed to be some inconsistency in whether the rear shelf was interfereing with the top folding. It was noted that starting in 03, if you had the Bose option, the rear shelf was redesigned and appeared to be thinner, which suggested Porsche knew the older shelf wouldn't work as well as they wanted.
http://986forum.com/forums/general-discussions/55569-replacing-boxster-convertible-top.html
Having just sold a 2003 with a rear speaker shelf that appeared identical to a 98-02 shelf, I, and another post, noted the top was not fully lowering, that the boot was still about a 1/4 - 1/2 inch raised and had to be hand pushed down to get flush.
The other 2003 I have does have a rear shelf that is NOT the redesigned Bose speaker shelf. Interestingly, the top opens just fine. So, now I don't know what to think. On one 03, the shelf seemed to interfere, on another it does not.
Going the other way, putting an 03-04 on to a 98-02 with a shelf, didn't seem to cause a problem. Leads me to wonder if the thickness of the insulation above the motor increased in some 03-04 models (perhaps a factory option to lower interior sound levels) causes the occasional problem.
Any ideas?
Thanks,
Joe