I've started a list of cars that have unique/bespoke custom parts. Not including the generic parts that most cars have or the standard stretched widebody.
RX-7 GT-X '90. Front, side, rear , spoiler X2.
Sprinter Trueno. Widebody, front, side x2, rear x2, wing x2, grill x2.
Corolla Levin. Same as Sprinter Trueno, +1 grill.
Both cars have different parts when widebody applied, 1x front and rear diffuser.
R32 skyline. x2 front, x2 side, x2 rear, x2 wing.
Skyline '71. Widebody, x1 front, x1 wing, x2 grill.
Swift Sport. Widebody (Gr4 style), wing x1
Focus RS. Wing x1. Wing removal
A45 AMG. Grill x1
S2000. Front x1, side x1, rear x1, wing x2.
300zx. Front x1, side x1, rear x1, wing x2.
Lancer Evo 4. 1x front, 1x rear.
Lancer Evo 5. 1x front, 1x rear.
Stratos. 2x front.
3.0 CSL '71. 2x front.
370z. 1x front, 1x side, 1x rear, 1x wing.
350z. 2x front, 2x side, 2x rear, 2x wing.
MX5 ND. 1x front, 1x side, 1x rear, 2x wing.
Mini cooper '65. Widebody, 2x front, 2x rear, 1x wing.
911 GT3 '01. 3x wing.
Supra GR. 1x front, 1x side, 1x rear, 2x wing.
BRZ Sti Sport. 1x front, 1x side, 1x rear, 2x wing
BRZ S. 1x front, 2x side, 1x rear, 2x wing.
Civic type R '20. 2x wing.
Integra Type R '95. Widebody, 2x front, 1x side.
Integra Type R '98. 1x front, 1x side.
R33 GTR. 1x front, 1x side, 1x rear, 2x wing, 3x grill.
GTR R35 '17. 2x front, 2x side, 2x wing, 1x grill.
M3 '07. 1x wing.
Viper GTS '13. 1x front, 1x side, 1x rear, 2x wing.
Mini cooper '05. 1x grill.
M3 '03. 1x front, 1x wing.
Abarth 500 '09. 1x front, 1x wing.
Work in progress of course this is just from my garage so far with still about 30 cars there to check.