I am not sure of my facts here........ but it certainly used to be the case that if you were Agricultural registered - you are not allowed to carry a load on the vehicle? People who have put load beds on Fastracks have been pulled over this?
Ok to tow a trailer with a load that is agricultural, but not a load eg a few bags of corn etc on the Ag vehicle?
There used to be a company which removed the rear tubs of Landrovers and put them back on QD as link boxes. Im not sure if this law still applies? but it would be well worth checking?