You can vote for encourage Forza to add these cars here. 
Acura ARX-06 : Acura ARX-06
Alpine A424 : Alpine A424 Beta (LMDh race spec) 2024
BMW M Hybrid V8 : BMW M Hybrid V8 (LMDh)
Ferrari 499P : Ferrari 499P
Isotta Frashini LMH tipo 6 : Isotta Fraschini Tipo 6 LMH Competizione
Lamborghini SC63 : Lamborghini SC63 LMDh 2023
Peugeot 9x8 : Peugeot 9x8 Le Mans Hypercar
Porsche 963 : Porsche 963
SCG 007 : Glickenhaus SCG 007 LMH
Toyota GR010 hybrid : Toyota GR010 Hybrid
Vanwall Vandervell 680 : Vanwall Vandervell 680 LMH