Fine Scale Modeler once printed an article about making working hinges for car trunks and doors using brass tubing and thin brass rod. I don't have the exact issue date with me now but I think it was about 1993. If I was at home, I'd check the issue date now as it's in the Jeep Cherokee kit box. I opened two doors and the liftgate on the Cherokee and made hinges per this article. They aren't ultra-accurate but they're durable and they work. Once you get your trunk lid hinged, you can add a spare tire, tire iron, toolbox and even junk to the trunk!