Series 3 109 fuel tanks

I just tried to fit the new 109 tank to my project and it doesn't fit at the rear mountings, are there more that one type of 109 tank?
looking online I can see the currently available tank seems to have an additional outlet pipe my original tank didn't have and according to the paperwork I have the correct suffix C tank. Looking at it everything seems fine but left puzzled on whether it is the wrong tank or the chassis is out. The tank looks perfectly fitted, just the two rear mountings are out by about an inch of so. Am I missing something obvious here?

it's a long time since I did my tank, but I think there may be two sets of mounting holes for the front of the tank, check that you're using the foremost. Dim memory, so I might be talking bollix.

I am already on the front of the two hole sets so it can't go any further. It also lines up perfectly to the chassis and crossmembers , its just the mounting plate at the rear seems too long.
Is there a difference between the two types of tank advertised, one is for all 4 and 6 cylinder petrol models and the other is for diesel and V8.
The 6 pot has a number of V8 parts fitted to it as standard but all the parts books show it has the standard tank and certainly thats what I took off, not the V8 Tank

A mate had a similar problem and just cut the bracket free and welded it back where needed. If everything else is right I suggest you do the same.

Everything else seems to measure out as OK, including the filler neck. Looking at the pics of the original tank it looks like the original one had a shorter mounting plate at the rear. I am starting to wonder if the V8 tank is the one that was fitted originally and what the mounting holes in the chassis are for, despite the parts catalogue saying different.

Mmmmm! I am spending premium time ( + blood, sweat and tears) resurrecting a 1979 LWB Series III that has been well messed about with in the past.

I have just removed the fuel tank (diesel). The from was secured by bolts/washers/ rubber grommets etc. at each side. The back of the tank has a bracket at the bottom which was welded to the plate that the tow hitch is mounted to.
(I have discovered the most valuable tool is a disk grinder with a narrow cutting disk; far less blood than a hammer and chisel!).
Question? Where on the back of the chassis is there supposed to be a bracket to which the tanks is supposed to bolt? There is no sign under the chassis but there is some welded debris on the top of the chassis that may have served the purpose but the bolts between the bracket at the bottom back edge of the tank and the top of thew chassis would need to be 10 in long! I have been looking at replacement tank pictures, new chassis etc but they seem to hide what I am looking for.
All and any suggestions gratefully received.

There are a number of holes at the front end of the x member, outside the box section, that the bolts go into. The first pic shows one of the holes in the crossmember, ignore the tank as its wrong

I just powdercoated all the new metal spaces for the fuel tank mount but even after looking at the parts manual and the repair manual, plus checking the interweb I can't find a definitive order to fit the rear bolts. I am happy with it all apart from two items, the two identical thick spacers on each bolt, do these go one on each side of the crossmember or both on the tank side of it?

I know this is an old thread, but for anyone researching how to do this job, I offer the following observations.

I had a similar issue with a 109 rear fuel tank. Lining it up with the front mounting holes, the rear mounting holes were a full 12mm to the rear of the crossmember holes. My crossmember and chassis were original and unwelded so it wasn't the vehicle.

After a lot of measuring and checking, I found a welder/fabricator to cut 12mm out of the mounting flange and weld it back on.

Cutting and shutting the tank bracket is exactly what I ended up doing, I also then gave the whole tank a proper 4 coat paint as the thin original coating of black was not going to stand up to much abuse.

I had the same issue. It was about 5mm.

I managed to get it to fit with sheer brutality.

Soak the gap between the cradle and the tank proper with decent anti corrosion wax.

Mins has four coats of paint as well as anti corrosion wax on it, including under the cradle as far as I could. Not sure how brute force would get it on, I had to cut and shut mine as the difference was fairly big. You can see how much I moved the bracket towards the tank in this pic, the edge of the oval was originally level with the mounting bracket you can now see through the oval hole!

My crossmember had also rotted out, so changes were made there. But brutality was involved. Still can't attach photos so not bothering.