Trying to do Modern African History

I am currently finishing up footnotes on what will be my fourth short piece dealing with Africa in some way. As long as I am in the history department here at University of Ghana it seems that such opportunities, usually book chapters, come about once a year. To date the chapter I am currently finishing is the only one to focus on Ghana. The others have focused on Togo, South Africa, and the Black Diaspora. Officially the Black Diaspora is one of the six regions of Africa according to the African Union, although much of it including the part I wrote about isn't very African. One of the problems with writing about Ghana is that I am far more interested in the early independence era than I am in the colonial era. Yet, almost all of the archives for the post-colonial era still remain completely off limits. The fact that Ghana has been independent for over fifty seven years now hasn't done anything to speed up the declassification process. I was told by K.B. Asante that it is unlikely that Ministry of Foreign Affairs documents regarding events in 1963 will be available before 2043. So while the current piece I am working on is about 1966, the local archival source base for Ghanaian history is largely limited to the years 1874 to 1957 when it was officially a British colony. That puts a lot of restrictions on the type of history that can be written using the archives here as a source. I am not sure what it is like in other African states. Do any of them have archives dealing with the post-colonial era that are open to historical researchers? Are they all like Ghana and basically only allow access to documents pertaining to the years that they were under European rule?