Vehicle doesn't change/What's a good way?

I'm trying to find a new way to create a vehicle dealership, it being custom, I thought of using NUMPAD 4 and 6 to swap vehicles, but when I do that, it only uses NUMPAD 4, and 6 doesn't work + the vehicle doesn't recreate (I apparently deleted the code last night too.)



So, in your opinion, what's a great way to for a vehicle dealership? Dialogs? Or what?