As stated I believe the '77/'78 lever can be used on a '76 as the spindle seems to bee the same part for all three. Of course my '76 parts bike has the teeth stripped so I cant get it on. HaHa. But the main point is the clearance on the later models - the "76 may not clear the driver foot peg on a '77/'78.
Thanks Kandrtech for posting my pics. May have been the size of the files, not sure.