Would a CDI box from a 1978 Yamaha Exciter 440 fit in a 1981 Yamaha Exciter 440?

From what I have read in the shop manuals for the 1979 and 1980 Exciters, there was a change between those 2 years where the CDI was not interchangeable due to the timing. So, I'm not sure how well it would run if you used one from a 1978 Exciter in a 1981 Exciter, or if you would eventually burn down the motor. However, if you have installed one, and it is working, then that's great.