You should watch 'Rockers', if you haven't yet, get to know a lot of movers and shakers from JA in the 70's in that film, otherwise i would check for Eek-A-Mouse, Culture, Revolutionaries, King Tubby, The Congos, Freddie McGregor, anything Studio One at that, Ras Michael, Big Youth,... there is a thread here on AG loaded with good reggae if I'm not mistaken... not sure where though..