I might have a look at those for my 1984 ex-military 109. I would like something close to the original military tread, but I don't suppose they are available nowadays.

You want deestone extra traction tyres. These are the same tread as the Goodyear extra grip originally fitted by the military.
 
What engine have you got ? As it affects your choice.
Not really, 7.50’s we’re a standard factory fitment on lwb for both petrol and diesel models the closest metric equivalent of which is 235/85/16. Unless you are looking to fit a non-series oversized tyre how does the engine make a difference?
 
OP has a SWB
Lwb and swb use the same engine, and lwb is heavier, so the engine will be more than capable of pulling 7.50’s. Whereas originally the swb would have been fitted with 6.00 tyres or metric 205’s they are not as easy to find anymore but the lwb 7.50 and equivalent are still common and regularly fitted to swb models.
 
I run 235/85 16s BFGs. 235/85 will fit the LWB / Defender rims and beceuse the rim is on the narrow limit for this size tyre they come out a very similar size to a 750R but with more choice.
 
I replaced my deestone extra traction for rangemasters was about £450 for 4 inc had Michelin tubes from ATS , so much quieter and better road holding
 

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