I tried one back in the day on a 74 XR75. Also tried to run one on my YZ80C. I never had success with them. My take is that they are a glorified chainsaw set up with dubious timing and advance control.
Unless you are going for the retro look, the sensible alternative is to get the straight bolt on CDI set up from a later model ('93 on) XR80 or, with a bit of adaption, from a CRF50.