Yamapag, the year of the engine has no effect on the charging system. Engines swap around pretty easy. You should check by year of the bike.
70-79 used the seperate regulator and rectifier, the 80 up used the combo reg/rec.
Another thing you can check is under the round cover on the left side of the engine, the one with Yamaha on it. It will look like this if a 70-79. It will have a reg and rec like these.
Leo