They are basically the same design, just different heat ranges available. If the plugs you are using now are right then leave it as is.
If you are changing elevation, fuel, or fiddling with your timing and fuel mix then you may want to consider a different plug.
If you are taking your car up to 7000 and lovin it I would think your plugs are probably the right ones.
If however you are having some negative symptoms then please let us no what those symptoms are.
Shane
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78’ SC 911 Targa - 3.2SS, PMO 46, M&K 2/2 1 5/8” HEADERS, 123 DIST, PORTERFIELD R4-S PADS, KR75 CAMS, REBEL RACING BUSHINGS, KONI CLASSICS
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