Hi Niels. Deep deep down under is NZ(if you have not guessed already). Your photo certainly looks like a Salisbury 7HA. Just drain whole in bottom and filler part way up the rear casing. Your car has the four speed rover box? Mine is a 77 with the LT77 gb. Yes the BTR may be too wide for your car but as I said hopefully won't be needed. To check bearings before ordering same just pull the axles (may need a slide hammer to do, one of mine was exceedingly tight.) then rotate the bearings with your finger to see if you can pick up roughness.
Replacing your lever arm shocks with telescopic is a massive improvement.
Just thought also to check if your tyres are not rubbing on the exhaust pipe because of lateral movement if the spring eye bolts are warn or loose. if happening you should be able to see the rub marks on the tyres.
Doug
from deep deep down under