I have a number of comments which, I hope, will clarify some of the questions brought up in this thread (sorry for the long post)...
>> Oz spec over spare wheel fuel tank as fitted as original equipment in Australia. Gravity feeds into main tank...
I am wondering if the chap Jim talked to is just using the term “gravity” different than we do. In any case, in Oz all of the 80 series sub tanks fitted to
petrol fueled engines used an external transfer pump to move the fuel from the sub tank to the primary tank, not a gravity feed system at all the way we (U.S.) use the term.
This in contrast to 80 series sub tanks fitted to
diesel fueled engines which all used internal fuel pumps (inside the sub tank) that transfered the fuel directly to the engine (such as Bill described). Also FWIW, all 105 series subtanks - petrol and diesel - used the internal pump setup, to the best of my knowledge.
>> ...George Scolaros excellent writeup... man thats a lotta work for 13 gallons of gas.
Actually, it took George much longer to do the writeup than install the sub tank. In fact, he did the installation - for the most part - in one afternoon. What took forever (many months, by his own admission) was gathering all the bits needed to do the job.
Of all the tasks we have have collectively attempted (heater hose, starter, springs, axle work...), installing a sub tank is far less tedious...
after all the parts have been collected
>> (Scolaro) ...also some recently added info concerning newer subtanks (from 105 series cruisers) being imported and installed.
Both of the 105 series sub tank installations that George was following have been abandoned. Technically, this was a very “do-able” job, but there were so many niggling little differences between the 105 and 80 setup that it began to be a PITA and not very cost effective. Details for the asking, but I doubt anyone else will go this route now...
>> Any guesses as to the weight of one of these (80 series) tanks?
26-27 lbs (12 KG), including fuel take off, gauge sender, & straps. If you are including the dual filler neck, add another 5+ lbs (2.5 KG). And, add to this the shipping container itself.
>> 50L OEM sub tank (roughly 13.25 gal). “Oz spec over spare wheel fuel tank as fitted as original equipment in Australia holds approx 55 lts, Toyota says it holds 65 lts...”
Yep. No one can seem to come to a common figure on the capacity of this tank. The 80 and 105 tanks, BTW, are identical in almost every respect - such that you cannot tell them apart at first glance - and their capacity is the same... and also debated. It looks as though it is time to “get off the pot,” and actually measure the damn thing...
>> So, you need a tank from Australia, dual filler setup, a pump, plumbing and wiring, for 13 extra gallons. Seems cool but I wonder, is it worth it?
...and an anti-siphon solenoid, the proper gauge sender, fuel filler pipe,
ad infinitum... and so, I wonder too. Carrying three jerry cans has got to be simpler, but as noted, would not be “as cool.” On the other hand, a good scavenger can do considerably better than some of the numbers Jim’s contacts have provided here. Perhaps Matt’s contacts can do better.
For one, I am I diehard scavenger. I am compiling the definitive list of bits needed for this project, including as many part numbers as I can identify, what OEM parts need to be used, what substitutions will work, and so on... but it will be at least several weeks before I’ll have all the info together.
Cheers!
R -
Couldn't someone just get the Toyota part numbers for the 50 liter tank/dual filler and order it from a source in Japan? 
. To prevent the resetting of the circuit you would need to supply constant 12v to it and not switched. And if you really wanted to get fancy you could use the low fuel dash lamp to indicate when the aux tank was empty by being on steady and blink when the main was low on fuel :G.
