I always had good luck insulating doors. Got that more "solid" sound and made for better speaker enclosures in every old car or truck I did it in.
Heck, when I first got mine I put in some 4" fiberglass batting insulation! Man, that stuff worked great. But it was a pain sometimes to keep clean, dry and in place.
But great for sound and sound deadening.
If your door seals can be removed without destroying them, I would try that to see if that's why your doors won't close.
The two largest contributors to EB door closing issues are a gummed up latch and too-hard door seals.
Taking the seals out lets you more easily align the latch position with the body lines, then you put the seals in to see if they cause trouble. Original seals were rarely an issue, but aftermarket ones are very often the main problem.
It's easy to feel the difference between old and new in most cases, but some are worse than others.
It's why we have a fit guarantee on ours. It's not that ours are perfect either, but at least you're not stuck with them if they don't work as expected. We just ask that you try them on first, before going to all the trouble to glue-n-screw them. Makes the installer a lot happier if they didn't have to fight one more thing on their Broncos!
Anyway, don't know if you have old or new seals on yours Andy, but those are the two most likely culprits on an older Bronco. We were just discussing the different ways of cleaning the latches, but the seals are either hit or miss. Lots of ways to skin that cat, but only a few things you can actually do to a poorly fitting seal to make it work better.
Paul