Not sure, in 18 years of Morgan's I've never locked one the way I see it saves a slashed cover or roof leaving it unlocked.
It's all about your own comfort zone though and where you live and or park up I suppose.
An alternative point of view is that with locked doors and hood up an opportunist may be put off. A determined thief would find (easily) a less damaging way of breaking in, and to a pure vandal door locks wouldn't even be tried.
