GU has mounts for factory subtank and very different to the way GQ subtank is mounted as GQ never came with one from factory. Also won't have same fittings to fit you existing sender guage etc , would have an aftermarket one.
Depending on final destination: All 1987 to 1997 GQ's regardless of fuel used had the option of sub tanks. It was maybe a case that your country did not get that option but the Middle East and Europe had the option on the very basic model all the way up to kings road. it was just a case of getting the kit and bolting it in.
As for the fuel sender unit you can get a after market one from any good marine shop or company that makes tanks. For the fuel you can use a Bosch 12v/24v out of tank pump and just pump over to the main tank buy using a switch in the Patrol. I have ordered the OEM tank, and stone guard and all the fittings from Nissan for 4.8 Y61 so I can copy it here and build my own tank and increase the size. I will be using only the OEM filler neck cap lock holder. My idea is that once it get down to 1/4 of a tank on the main tank I will just pump over from the sub to main tank. Once I know how much it records I wouldn't even need a sender unit, timer, guage or anything technical. It can be done just by using the main fuel tank gauge.
I think a stainless 2.5 or 3mm GQ sub tank could be built for around 250 USD with the sender flange with two baffle plates inside and double skin bottom with Kevlar skid plate. I would maybe ask around as any fabricator can make these tanks. The flange for the sender unit. Just go to any good machine shop and they machine one for you in few hours if you have a sample.
Yeah ok thanks guys.
Apart from the factory mounts in a gu would the profile of tank fit? I can cut mounts off and re weld where required.
Wiring up things wouldnt be a problem I can get around that easy enough
Should not be a issue if you can weld and cut metal. The OEM tank is quite thin (Can not recall if OEM tank is alloy or Metal im sure its alloy so cutting that is not ideal). So maybe weld on extended panel plates to the tank with support lugs for bolts. Then you can make brackets / bolt lugs on the Patrol so it all bolts in. For the rubber spacers use OME shock absorber bushes as the ID hole is perfect for the fine thread and size of bolt you plan to use.
I'm still looking at self leveling tanks so i don't need anything just a sub tank. The only issue I have to get sorted out is the angle of the sub to main as its lower. The line connecting the tanks together would need to be at the bottom of both tanks to keep them balanced and the fuel injection pump will need to have a cross over. All to complex I think I hate the idea of the valve at the bottom of tank for several reasons.