I purchased some struts some time ago trying to keep with my theme of period correct performance parts. And to my shock I had some extra parts in a shed. One of which is a full set of Interpart Mulholland struts. These were sold in the 70s and the 80s as a aftermarket upgrade using oem springs or their lowering, stiffer springs.
they have seen better days but considering they are 30yrs old they still look and operate quite good.
The internal of the strut is oil filled not gas filled. Unfortunately, once these go bad they can not be rebuilt. Although there is a way to rebuild them but it required a lot of work and if not done correctly it can be a pain and also not give your Datsun a proper balance.
If anyone is interested in these struts do feel free to email firstname.lastname@example.org or take a look in the classifieds.