I can tell you that an early center screen will NOT fit an '87 GT5-S with late side pieces. I've not tried the early side pieces themselves but with careful trimming of the sheet metal edges, it might (heavy emphasis here!) be possible to fit all-early stuff.
Personally, I'd contact a European seller such as Roland Jaeckel in Germany, or one of the British or Swedish web sites. There are far more GT5 parts over there than here, and dealing with known Pantera people is better than haunting E-Bay and hoping.
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