In those days there wasn’t a standard rear light bracket , mudguard , run up ramps etc
Where I worked in 1980 the tractor units were delivered chassis cab with the rear lights on temporary brackets .
We manufactured all the components except the 5th wheel , guessing the work otherwise was done by local bodybuilders .
Now because of type approval it seems the lorries now come from the factory ready for the road just put the stickers on and away you go !