Question1: if a HQ 1 tonner cab with HQ tags from 1971 go onto a late WB chassis from 1984, what ADR's does it have to comply with?
it has to comply with the adrs of the chassis.

Question2: If your answer to question 1 was the WB ADR's, how would some inspector at the inspection station know if that chassis was a 1980 chassis or a late 1984 chassis? and hence 1980 ADR's or 1984 ADR's?
because rego authorities have computers and wb has chassis numbers awb bwb cwb dwb for the years.

Question 3: why wouldn't the 1 tonner in this configuration have to comply with the ADR ID tag on the cab, - the 1971 HQ ADR tag, as there is no WB ADR tag in sight......
because in nsw the tag isnt recognised as it does not match chassis number which is the legal entity of the vehicle

Question 4: why are HQ 1 tonner compliance tags worth more than all the others???????? hint - pre pollution Chev.
hq tags are worth nothing if attached to said wb..chassis number is what its regoed from ..hence hq