I think all the Honda coils with screw on wire caps run much lower resistance than those for sohc4s. Using them with sohc4's would result in excess power consumption...it will charge the battery weakly or not at all. I was once told that Yamaha rd350 coils can be used on a 750...never tried it.
Some report that Dyna 3 ohm coils work ok, some have charging problems. Dyna 5 ohm are known to work and a good stock coil typically measures about 4.8 ohms. So if you want to start measuring, don't try to use anything much below 3 ohm.