Are you going to do long journeys in one day with veg oil ? As you say a lot of weight to carry as a rule Mercedes sized the tanks for one days average use surprisingly small tank if that's the case, One of the reasons the 404 has two small tanks is the flex in the chassis.
It is possible but will require some engineering and consume space.
Moose
We think that, as with seemingly everything for these fire truck 'Mogs, the fuel tank is a custom size - we were surprised by its size as we were expecting the average size Mog tank, but it's a 90 litre tank and unfortunately the way the filler spout is attached means that it's virtually impossible to actually get 90 litres in it. Barring its temporary use as an aid to our house move, we shouldn't be making enormously long journeys in it - maybe into NL or Germany for various dog events, and dotting hither and thither on rallies etc. So perhaps this is a project for another time...
Cheers for the advice guys!
Rob & Sue