Hey mate,
I also have a tank from 4wd system. I rang up to order the 145l tank, and asked about getting it customised to suit my body lift, and within 5 mins I had spoken to the guys that actually weld them up. Ended up with me getting a 180L tank as they could extend it for me with no hassle what so ever. Can't remember what extra it cost me, but it was bugger all. Think it was about 80 bucks on top of the 145L, which at the time was somewhere around 800 bucks.
Turned up well painted, and prompt delivery. Definitely flush the tank out, more than once, to try and get as much of the crap out of the tank as you can. They can not flush it out for you with fuel as then it becomes a dangerous good to ship as it has had fuel in it, so there is a reason they can not flush it out for you. But remember there is a lot of baffles and cut outs etc in there, so make sure you are thorough, and I then changed my fuel filter after one tank fuel, then did another filter after another three tanks I think, just to make sure. Couple of filters is a small price to pay I figured. (And I did find a lot of metal filings etc in the filters....even after a few flushes. Thats what a filters for tho..)
Yes, I have had problems with a weld leaking, and they were very quick to try and sort it out for me, offering to pay for it where ever i had to get it welded ( I was in remote north WA) but it was not a major leak, and was where the front mounting tab was welded on. I still have it on my project list to modify this mount to make it stronger, but long way down the list.
But have so far not had any other problems with it, apart from the mounting bolts coming loose. I recommend loctite threadlock on the bolts. Also the exhaust will come with in millimetres of the tank, so you might need to modify the exhaust slightly (I had a flangejoint right underneath that had a visit from a grinder....) And it does hang lower than the longranger tanks etc, which they originally said it wouldnt, but I just have to make a bash plate up for that front corner and there will be no worries.
Good price compared to others, good service, looks good, and fits really well (Once you take the tailshaft out etc...)
End of a long story, I love the tank, except when I have to pay the fuel bill at the servo, and can't believe how I used to have to fill up after every 550km or so before.... but given its one tank not two, it will suck if I ever stove a hole in it, hence I still carry a jerry with me as well when I go bush.