Too bad there's no way to hack the game itself to make these cars accessible on a real console.
Well, as I just discovered, a hack isn't needed. The game has a few
debug codes. At the title screen, after the title music just starts up (you can't enter the code when the wind is howling or when START/CONTINUE is on screen), press the following buttons the specified number of times, then press RUN to choose start or continue.
Ux5, Dx9, Lx6, Rx0-5.
Watch the Ending using the car specified by R button presses. 0=Citroen, 1=Ferrari, 2=Lambo, 3=Porsche, 4=Acura, 5=Renault.
Ux7, Dx7, Lx7.
Watch the Credits!Ux3, Dx8, Lx4, Rx0-16.
Stage Select.Ux9, Dx6, Lx8, Rx0-5.
Car Select! As in the main game, 4 and 5 button presses get you the Citroen and Renault.
Ux10, Dx0, Lx9...
?
Ux4, Dx2, Lx10...
?