The problems with water or condensation in distributors is all about the high tension side. Whether it has magnetic trigger or old fashioned points don't make much difference, ask a 3.9 driver (which has magnetic trigger as standard)!
Mallorys are nicely made, so that gives it a better chance of sealing ; reckon you'd still do the usual of applying silicon grease to seal the cap edge and arrange a through ventilation for the body.
cheers, Ross K
