I just replaced all of these hoses on my 87 325. Look up the diagram on realoem as suggested. There are 3 hoses that travel from the overflow tank/filler neck, behind the shock and through a hold in the inner quarter through a pipe then connect to the tank and other hoses in the hatch under the rear seat. It was a hell of a job. The hoses were rusted to hell and I had to cut the pipe inside the car to get them out. The hose cover inside the wheel well gets rusted to hell. There is a tee connection from the overflow tank to the larger hose that rusts out as well. If you fill your tank full, it will spill out. If you fill more than 3/4, it will smell until you run the tank down a bit.
These are the hoses you need:
16121177553 - fuel hose 14 x 20mm - filler neck to fuel tank - $20.75
This is a flexible braided line
There are also 2 other plastic (vinyl) lines running through the tube coming from the overflow tank above the well liner. 5/16" and 1/4" outside diameter. Got the 5/16" from a local parts store and the 1/4" off of eBay. I strongly suggest trying to salvage these. Unfortunately I damaged mine trying to get the braided line out.
All 3 of the lines connect in the hatch under the back seat.
I just happened to have snapped some photos of the finished product.
In the first pic you can see the new tee. I just found a plastic one to fit the main line then improvised to tee off to the overflow line above.
The second pic shows the hoses in place and taped together. You have to remove the top shock bolt to get it out of the way.
The third pic shows everything back together and coned up real good.
16131179011 - wheel well fuel line cover - $40.95 (ouch!!) says it's plastic but it's metal. Bav Auto was the only place I could find it.
Hope this helps.