Way off topic -completely - cleaning a diesel fuel tank

[gldgti]

OP - for just cleaning the tank, I would use petrol. Once you've cleaned it out you can leave it in the sun for a bit and any remaining petrol will evaporate. I find petrol or turps the best for cleaning old dirty engine parts and tanks.

After I'd cleaned it with petrol then I would do what transporter said.

[Highlander]

No, it is on topic.

I would use interject Diesel Cure and Care, it is very powerful biocide additive. But, it might be a bit difficult for you to get, so the Fuel Doctor made by Castrol or Wynns makes additive with biocide, I saw at Sprint Autoparts for a very good price. Furthermore I would make sure that there is no rust inside the tank. Installing additional fuel filter with the glass bowl is good idea; Ryco sells one (around $60)

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Fuel must have been ordinary 50 years ago too. Original engine has both primary (cartridge) and secondary (bowl and gauze) fuel filters.

And found the local Interject dealer (via Google) less than 10km away from the farm so looks like I will try your first suggestion. Link for anyone else who may be interested

INTERJECT INTERNATIONAL

Thanks again