I'll let others answer more on the use of the Harley Coil but from a personal experience I can say that doing just the opposite worked for me.
See I was having an ignition problem with my 1988 Sportster and was not sure if it was the coil breaking down after a short time running or the ignition module failing. I checked the coil spec's between the XS650 and the Sportster coils and they were very close. So I temporarily mounted a spare XS650 coil to the Sportster for a test run and sure enough ignition started breaking down at the same run time.
Then I replaced the ignition module and Sportster ran good after that. I think to some extent a coil is like a light bulb, as long as the resistance, voltage and such are close it should work. Maybe at the extreme ends of performance one might see a difference but for the most part that would not be noticeable.
Of course you would need to wear a beanie helmet when riding with the Harley coil!