Ok so its a carbed MWB which makes it a FJ73. You will be struggling to get better than 17 mpg regardless of what you do.
Im not too sure about doing a gas conversion on an engine with high klms.
I would not do it for a number of reasons and the main one being the cost.
It would set you back about $3 grand.
The LPG tank will only fit where your old tank is and will hang down 100 mm lower if you want the same range as your petrol tank.
Then because you cant refill with LPG away from the petrol/LPG station you will need an auxillairy petrol tank mounted forward of the rear axle.
Thats if you want to go a fair way off road.
The hiclones are a con. I had one on mine when I bought so I trialled it and it didnt make a bit of differnce,not even 1-2% over 3 months.
The carb rebuild may help but if its running ok and your plugs are clean then it will only be a minimal improvement.
Ok so what do you do? The cheapest way would be to sell it and get a diesel 4x4,but you like you like your MWB too much RIGHT

The next best and cheapest option would be to install a diesel.
There are lots of cheap 2H 6 CYL Landcruiser diesels in the Quokka classifieds and they will fit straight into yours without much trouble.
There has been one for sale there rebuilt 40000 kms ago complete for $2k.
Still cheaper than LPG and you would have a real HJ73
Here and the diesel tech forum will be your best place for advice.
Is that your real name?
