I have configurations of vehicles that I want to post, but they use modded content. If I post the configurations, then will they work if downloaded, even if the mods I used to create them aren't included?
No, they won't work unless the one receiving the config happens to have the same mods too. If you do post a config, I would recommend posting links to the mod page/resource the config requires. --- Post updated --- At minimum, put a list of mods used for the config.
First, get the mid authors permission. If they say yes, move the content you used into your mod. Give credits and you won't have a problem.