Nice find! Best off cleaning it up best you can and keep it unrestored as it looks very original. Other than that, dig in deep and rechrome everything. Japanese chrome was shitty in the 70's.
Here is my '77 rd400. a lot of fun around town. So many people want to talk about them. I always wanted one in Highschool. After getting one and owning a Blackbird I just shake my head. Oh the 70's.