When you say stage 3 do you mean dna filter? If so before worrying about gearing I would ditch that and go with a sealed air box and foam oiled filter. I don't have any direct experience with the Simpson but in the sand a fatter front tyre, upgraded suspension and rim locks to help with the lower pressure would be more useful I believe. I have mucked around with a few different gearing options and always end up going back to stock. IMO Once u have a exhaust fuel and O2 mod and a good filter set up I find standard gearing the best all round. However I did prefer my 14tooth front sprocket off road but it was to much of a compromise on road for me. Good luck with the trip mate I'm jealous and would love to do it some day.

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