So they added the ability to number cars ... and limited it ... again. For the love of all that is holy!!! I realize that this is a "Driving Simulator", but some of us are trying to use it as a racing simulator. F.
They added it back in GT2 (I think) back when you could RM cars. It appeared again in GT5, limited to a small number of street cars, then there was a DLC with Touring cars that were just pre-made RM's. Now they've given us Base Models - race cars with no livery, which we can paint in a colour of our choice and number of our choice.
The choices are actually not that limited, really.
This is the list of cars from the Car List that we can change race numbers on:
Autobacs Garaiya GT300 Base Model '08
BMW M3 GT2 Base Model '11 (not in the game though)
Honda HSV-010 GT Base Model '12
Honda NSX GT500 Base Model '08
Lexus IS350 GT300 Base Model '08
Lexus SC430 GT500 Base Model '08
McLaren F1 GTR Race Car Base Model '95
Nissan GT-R GT500 Base Model '08
Nissan GT-R NISMO GT3 Base Model '13
Nissan Z GT500 Base Model '06
Peugeot Peugeot 908 HDi FAP Base Model '10
RE Amemiya RX7 GT300 Base Model '06
Renault Sport Mégane Trophy Base Model '11
Subaru BRZ GT300 Base Model '12
Subaru IMPREZA GT300 Base Model '08
Toyota 86 Race Car Base Model '12
Toyota Supra GT500 Base Model '05
Volkswagen Scirocco GT24 Base Model '08
Acura NSX LM Race Car '91
Audi R10 TDI Stealth Model
Chevrolet Camaro SS Touring Car '10
Chevrolet Corvette Z06 (C6) LM Race Car '06
Chevrolet Corvette ZR1 (C6) LM Race Car '09
Citroën GT by Citroën Race Car
Dodge Challenger R/T Race Car '70
Gran Turismo Red Bull X2010 '10
Gran Turismo Red Bull X2011 Prototype '11
Honda CIVIC TYPE R (EK) Touring Car '97
Honda CR-Z Touring Car
Honda INTEGRA TYPE R (DC5) Touring Car '04
Honda NSX GT500 Stealth Model
Lotus Elise 111R Race Car '04
Mazda 787B Stealth Model
Mazda Roadster Touring Car
McLaren F1 Stealth Model
Mercedes-Benz SLS AMG Stealth Model
Nissan GT-R GT500 Stealth Model
Nissan GT-R R35 Touring Car
Nissan SILVIA spec-R AERO (S15) Touring Car '02
Nissan SKYLINE GT-R R32 Touring Car
Nissan SKYLINE GT-R R33 Touring Car
Nissan SKYLINE GT-R R34 Touring Car
SRT Challenger SRT8 Touring Car
Subaru IMPREZA Sedan WRX STI Rally Car '05
Subaru IMPREZA Touring Car
Suzuki Cappuccino (EA21R) Race Car '95
Toyota PRIUS Touring Car
TVR Tuscan Speed 6 Touring Car '00
Volkswagen Golf IV GTI Touring Car '01
I think maybe the karts can have their numbers changed as well, but I'm not sure.
That to me is a lot of cars that we can change the numbers on.