Out of curiosity, is there a place where they're permanently on-display in Japan? Or are they only used as temporary exhibits? As I'll be heading over there soon, I'd love to be able to see some of the props in person. From my own research, there's the Toei Kyoto Studio Park and Toei Hero World, though they don't appear to have a complete collection.
You can see my photolog of my recent trip to Hero World. They have a warehouse there that stores many costumes, and the rest are generally kept in the Toei warehouse, as I understand it. For example, they have a storage situation for sending things to the US for use in Power Rangers.
The first time I went, there were several adult fans taking close-up photos of the suits. The second time I was the only adult, but the man playing Musashi Ghost was very kind, and interacted with me a bit for some pictures. You'll feel fine there, but brush up on your Japanese, because there's a lot of menus and questions when you want to get a ticket. I think there's four different kinds of tickets, plus buying the exclusive Eyecon and that stuff. Anyway it's a really good time there.