I have considered using light weight aluminum to make a "box" around the hinges that I can put through the hole. I fear that the hole is too small to put anything solid through it, however. The Cosworth Pinto doesn't even have a heater, but I don't really want under hood gases seeping into the interior, which I fear will happen without some kind of seals at the hinges.
I've seen people say some Fox-bodied Mustangs use a similar boot, but it "doesn't fit", citing bolt hole differences, but no other details. I'd like to investigate if there are other insurmountable reasons why they won't work.
I threw away boots I had on hand a long time ago, thinking I could purchase new ones once I needed them, so I don't even have old boots I can repair enough to use as a mold for making them out of spray plastic.
Now I'm just hoping we can persuade some company like Steele to make them for us.