In all fairness, the 1997 - 1998 gen of GT1 is kinda right on there. The Legion GT1 is the CLK LM bang on and URD has the CLK GTR so there's that. The Esperante GTR-1 is already in. F1 GTR Longtail is also in, 1997 spec R390 GT1 is in there, Elise GT1 If you want to do the original GT1s from 1994 - 1996 the Kunos F1 GTR is there, the Skyline GT-R LM on RD, the Supra by zi5ki, Sard MC8 like you said, URD's 911 Evo, and AL/AG's 911 GT1 from '96.
massive TL
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Legion GT1s already in:
CLK LM, 911 GT1 '98 spec
TS020, F1 GTR LT
Elise GT1, Panoz Esperante GTR-1
F50 GT and the R390 GT1
97 - 98 cars needed in
CLK GTR, 911 Evo
Lambo diablos (can't put my head round which ones)
Lister Storm GTL
Panoz Q9 (kinda in as it's just an esperante)
Quafie R4 (on AL)
94 - 96
Alpine A110, EB110, C4 ZR1
F1 GTR (kunos), R33 GTR LM (RD)
SARD MC8, Viper GTS-R (AL or RSS)
Marcos Mantara + LM600, F40 LM/GTE
Honda NSX, Jaaag XJ220
Lambo diablos (similar to 97 - 98)
Lancia 037, Espirit
911 GT1 and other 911s
Supra, Venturi
https://www.dailysportscar.com/2020/05/24/all-the-gt1s-every-make-and-model.html - use this as a guide to know where goes where this is what i used for you lot.