Nope.
Thinking of one grade thicker. Already, if there is any extra weight, bar my excessive 20 stone (approx

) the diff will hit the removable cover board over the rear axle on the '76.
So if I'm off on a photo session with most if not all camera gear, or with SWMBO, or we go away for a few days/week there is quite a lot of contact between diff and board.
Mind you, my dampers might need a bit more of a tweak (replacement?) than just heavier oil... Or better still perhaps I should lose a few stone!

Cheers,