Hi Yozzer
I've been looking at this since I need to replace both my coils at some point because they're old and knackered. From what I've read they will work but the original ignition system prefers higher resistance units (specifies 5ohms I believe). I've not found any newer coils that are 5ohm, however. The only potential drawback is that they will pass greater current and, likely, reduce the life of the points to some degree. That's all I've managed to discover so far. I think when the time comes I'll probably replace both the coils and the ignition with matching parts.