Just trying to get some ideas together. What kind of struts (rating) would I need to get for something like this? I know the shelves alone are going to have some weight to them, plus all the gear I'll be carrying around.
From this page, you ought to be able to narrow it down to two or three realistic choices. Buy all three and return those that don't work.
Gas struts have to be selected carefully. If you get struts that are too strong, they will open the lid like a catapult. And you won't be able to close it without a winch.