Has anyone made maps of the hitboxes to trigger chests in each stage? I'm learning the game and it seems like it would be a really useful resource to have on hand.

VGMaps have chests in their maps, but they're missing a couple of them: http://www.vgmaps.com/Atlas/SuperNES/index.htm#SuperGhoulsNGhosts

I've also made a lua script for bizhawk which displays the chest triggers: https://pastebin.com/HAvi3MdT

Finally, I've made a series of tutorial videos which are played with the above mentioned script. They're rather long however and more meant to document the strats I've learned, so probably not your best bet if chests is the only thing you wanna know.