Tell her it'll be worth more if it's a HJ. You've got the rare expensive part, whatever you spend on a Hj chassis/ tags you'll probably get back by selling the HX chassis/tags (or even better, buy a HX Kinga shell and flog the whole lot off as a complete car.

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PS. Most women struggle to see the big picture when it comes to these things. They'll happily spend money on a fast depreciating asset but don't realise that pile of old junk will at least hold its value even if it sits there for a couple of years.