Hi Romain,
To assist with your search, I believe brake parts were unchanged with all SD1s with the exception of the later Vitesse/VDP Efi cars which had uprated four pot ventilated brakes.
Hence I think the brake parts you seek need not be specific to the 2600 (Series 1?) model you own.
Additionally I believe the 2300/2600 76-80 tail pipe is the identical part to the 3500 1976 to 1982 (Rimmers Part No: GEX3782), therefore this again need not be specific to your 2600.
Series 2 cars tailpipes however varied quite significantly.
(Please correct me if I'm wrong chaps.....)
Good luck with your search.
Jay
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Lifelong SD1 fan - 1983 Rover 3500 Vanden Plas