If you are agreeable to a space saver size spare, one will fit in the ERA standard trunk in the lower space. You could use straps, or even just lay it in there. It's small enough to still allow you to actually use your trunk, unlike a full size spare. The floor of the 427 ERA trunk is usually at a level just below the trunk latch. If you think you need a spare tire, you will also have to secure a jack and a hammer. If you are using 6 PIN wheels I have a spare that came out of an ERA 427 that I would sell.
The photo below shows the spare I have, but this is an FIA pictured, not a 427. As stated before, it fits perfectly inside the 427 trunk. It's currently painted with plastidip and can easily be peeled off.
