Convert Tdi Fuel Filler To A TD5

At present the fuel filler on the wifes 90 is in the rear truck bed as it's a TD5 bed/boot on a Tdi/chassis. Is there an easy way to convert this to fill through the existing TD5 filler without having to change the tank/bed or cut a hole where the fuel neck on the rear panel should be? I hope this question makes sense to you all. Apologies if this has been asked before, I did a search but couldn't find anything.

Thanks in advance to anyone kind enough to help.