In theory they should at least be straight (consistent gap top to bottom) but like rodeo said, there are so many different gaps on different Broncos, it's hard to pin down.
And with so many years of spilt milk under the bridge on these things, multiple removals and replacements of hard tops, installation of soft tops and bikini tops, accidents and general mayhem, an original gap is very unlikely to still be there on most EB's.
But Steve83 here does have some diagrams on his SuperMotors site.
And I'm pretty sure some diagrams have been bandied about here on the forums over the years too. Maybe someone with good search kung fu will be able to help with that.
There is also a "Ford Body Book" that many have bought that might also have gap info. I'm not sure, because I've never seen any info that helped me with those kinds of questions, and it does seem more of a general assembly book without the finer details, but someone that has it might be able to find something.
In the meantime, my '71 has good gappage and I'll try to get a measurement for you. I believe it's less than a 1/4" all the way up though, and the weatherstrip bits in that area completely fill it up flush.
I've had the top off and back on numerous times over the 42 years I've owned it, but the body is surprisingly straight and tight still.
Good luck.
Paul