35 inch muddys on a troopy

I would imagine they will as you are effectively changing the gearing. Wouldn't imagine it would be much though.
You will likely notice it isn't as quick off the mark and hills might slow you down a bit more as well.
Increasing the width of tyres usually makes a bigger difference as it increases the rolling resistance as does tread type, the more aggressive the tread the greater the rolling resistance.

I would first check if they would fit, I don't believe they would fit on my old girl.

I run 285/75/16's and they don't touch but I think anything else would without a body lift and maybe offset rims.

Fuel will only get worse as Peter said, you also will be changing down quite a bit more.

I have not upgraded to 35' tyres before, but have gone from the standard 31" tyres on Patrols and Cruiser to 33" tyres and kept fuel consumption data. I have found (not saying this is the case for all vehicles) going to larger tyres does not affect the fuel consumption a great deal, but 35's may be different. Going from AT tread to MT tread does increase the fuel consumption a bit.

Snowy

35s usully rub on the rear of the front wheel arch. It can be cured with a hammer.
IMO 33s are the perfect tyre to run on 75 series.

What sort of EGTs are you pulling now?

You may also find an increase in braking effort is required to overcome the loss of braking effectiveness caused by a larger rolling diameter wheel. Only an issue if you need to quickly stop though!! Cheers

It may also not be legal...... ;-)

Cheers,

Mark