better buy a tank with the right dimensions new or build a new one,
chopping and joining and old tank is a huge hassle.
Safety foam filled then you can forget it for 40 years.
 
eg.
http://www.ebay.com.au/itm/WDP-ALLOY-FUEL-CELL-76L-20-GALLON-WITH-CAVITY-SUMP-W-FUEL-SENDER-SA002258-/231386095105?pt=LH_DefaultDomain_15&hash=item35dfaf9e01
 
http://www.ebay.com.au/itm/AEROFLOW-FUEL-CELL-BLACK-ALLOY-57-LITRE-with-FLAT-BOTTOM-FOAM-AF85-2151ASBLK-/360946232365?pt=LH_DefaultDomain_15&hash=item540a126c2d
 
my fave with removable top
http://www.ebay.com.au/itm/RCI-16-GALLON-60L-ALLOY-CIRCLE-TRACK-FUEL-CELL-RCI1162C-RED-25-x-19-x-11-/141569329547?pt=LH_DefaultDomain_15&hash=item20f630898b
 
all cheaper than getting someone to make a new one somewhere
 
here is a list to choose many sizes of the RCI circle track ones
 
 
and a more comprehensive list here also but from states as well
under title RCI fuel cell

Do what I do and keep a couple of 20ltrs jerry cans in the boot.

You dont want to stop and fill undestandable
however uniting 2 petrol tanks is hard work
and be prone to leaks or safety issues in time
Whats the width between the rear and height
without worrying about the speakers however
considering the boot mechanism?
 
Heres another list and also consider a lower
weight to the ground setup like a drop tank
Ive always found the wheel well a horrible
rust gathering area that needs a drop tank.
 
http://www.ebay.com.au/bhp/fuel-tank

Original tank width is 85cm x 10cm high x 10cm wide at the widest point (botttom)
If you measure the top of the tank its onlly about 5cm wide before you start to intrude into the boot space.
 
I dont mind losing some space, but i do still use the boot for the spare wheel, jack, tools and some spares.
 
Had another trawl though ebay with the links you sent D
 
Found this unit
http://www.ebay.com.au/itm/RCI-RCI1211C-22-Gallon-83L-Poly-Circle-Track-Fuel-Cell-Size-33-x-17-x-10/321405770496?_trksid=p2045573.c100033.m2042&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20131017132637%26meid%3Dd1f4921fe104404eafe8ac0dd3422c59%26pid%3D100033%26rk%3D1%26rkt%3D4%26sd%3D321405770496
 
Its very close to fitting in under the parcel shelf as standard, but it would take up the entire boot space.
 
I think ive got a wagon fuel tank in the stash, so ill see if that fits into the wheel well as mentioned.
 
I could just use a jerry can or boat fuel tank and plumb that in with a small electric pump.
 
The solution has to be simple to use else its pointless. using a jerry can, means that I have to open the boot to fuel it and when im low, pull over and pour it into the tank. Im not that far from servos that i need the extra range, its all about convienence.
 
This sort of thing might be good
http://www.ebay.com.au/itm/Outboard-boat-Fuel-tank-Marine-uni-fit-25-litres-NEW-/111433812647?pt=LH_DefaultDomain_15&hash=item19f1f90aa7
 
its cheap and comes with fittings. Just need a pump and im away.
 
Alternativily, I could try and mount another sedan fuel tank into the boot. Mount it hard up against the original tank and double the capacity to 60l total. That might be a winner.
 
As for space under the parcel shelf.
As the tank is a rhombus to tank advantage of all the available space, a square tank doesnet really fit very well.

I didn't get time today to play with this idea at all. I spent my time replacing a blown headlight...
My father is coming up tomorrow night for me to fix his spare wheel carrier so I might get some time in the shed then to at least eyeball in a second tank and see what happens.


I wouldn't be too hard to mount a second sedan tank as I could just use flat bar to extend the original mounts and its completely removable.

As for filling from the outside, I'm thinking if I make a y-piece in the flexible hose then both tanks are filled from the same filler neck, much the same way that many Prados are.

Then its just a matter of hooking up the electric fuel pump to push the fuel over to the main tank when I get low. That's just a simple switch on the dash somewhere.

Now, for this 85 litre tank you talk of..... any pics or more info?

My fuel tank is about 60l.  We used 25l in 100km once so had to do something about it.  The factors limiting the size of the tank is the height of the filler tube, mine has been raised as far as possible under the original flap and the size of the boot lid.  Mark in Research.