Condensers and what a difference 3 mill makes!
If you buy a new Lucas condenser (OEM part number: 425377) for your Cub, you may find you have problems with the thread and nut that holds the end of the contact breaker spring touching on the casing causing it to short out. The problem being the new condensers are 3 mm longer than the original ones.
But what can be done about it?
It may be possible to file the thread down and chamfer the nut just enough to clear the casing, even pack a thin piece of insulation between the screw/nut and casing.
But another way is to fit a remote condenser next to the ignition coil under the seat, thereby bypassing the problem for good.
It needs a replacement bracket making to fit in place of the condenser, which will hold the contact breaker spring.