I got replacement parts, I think they were genuine Land Rover ones and not too pricey and it saved having to bend them to shape. I bought them from Dingocroft in High Wycombe (01494 448367) who posted them out.
I think, but I could be wrong that the plastic tanks are different, having the higher level filler (i.e. not just behind the rear wheel). The mountings may be different too. On the steel tank, you have two parts, the tank itself and the stone shield. The mounting bolts go through both, the plastic one may have straps to hold it on.
I strongly recommend cutting a hole in the boot floor when you've got the tank out, the article on www.rangie.com says that if you're brave enough, it can be done with the tank in-situ (I wasn't!), but at least now I can get to the pump. I cut a square hole and used a couple of bits of steel strip pop rivetted to the floor to hold the cut out in place. It now just drops into place from above and some gaffer tape seals the gaps. Not elegant, but it works. If you're flash you could cut a circular hole.
Note that with the EFi, you have the multi-vent tank with four small venting hoses near the filler pipe. Earlier carb. Rangies have the single vent tank