Axes

Three frames; don't mix them up:

Where	Axes	Units
Blender	+X the vehicle's right, +Y its front, +Z up; the ground at Z 0, the origin under the middle of the wheelbase	metres (1 m = 1 block)
Model frame (VehicleSpec, the steering wheel's and gear lever's points)	+X right, +Y up, +Z back (front −Z)	metres
Vehicle frame (VehicleLayout.Box, Seat)	forward, right, up	metres from the ground under the vehicle

Blender to model: (x, y, z) → (x, z, −y). The export script converts.