The specs you need to comply with are in particular VSI 06 and VSI 09

http://www.rms.nsw.gov.au/roads/safe...fications.html

For Bullbar compliance check this spec sheet
http://roadsafety.transport.nsw.gov....tolerances.pdf

Can't find any thing specific about the gas bottle but suspect it has to do with carrying flammable gas 2 on the rear is against safety regulations.

Not sure who does certification - you will probably need to do a swerve test etc Miraz (Geoff) might be able to help.