How far can you go with interior mods?

[crankit]

Does anyone know what the limits are to modifying a factory interior without having to get engineering certificates or the car being un-roadworthy?

I'm good with fiberglass and wood from boat building and I was thinking of making my own center console and maybe modifying the dash of my old column shift ute. Possibly even going so far as to redo the hole car including custom interior.

[Bushbasher]

I think so long as the seats are bolted in using the factory anchor points, the seat belts are as they should be and airbags are there and functioning you can go your hardest as long as it's all secure. I'm sure someone will correct me if I'm wrong.