Here are two binds, one to get into your vehicle and activate FPS mode, the other to get out of it and turn on action mode. Replace action in the yellow text if you wish to have it enter another control scheme instead. Both will adjust your field of view. Remove this if you want to avoid the change.
Right click inside the reticle to enable mouselook. Again to deactivate it and access the UI.
These binds both toggle your vehicle when it is in slot 1. The first bind will throw a message on your screen that you have used it.
Note: the offset for over-the-shoulder is finicky and only works sometimes.
bind numpad7 "InventoryExec 1 Devices 0$$schemes_setcurrent shooter$$gfxsetdefaultfov 40$$camoffset 3$$NotifySend 4 "Vehicle Mode Active" 0 LookModeReticle"
bind numpad8 "InventoryExec 1 Devices 0$$schemes_setcurrent action$$gfxsetdefaultfov 0$$camoffset 0$$suspendforcedmouselook 1$$camdist 25"