One of the reasons the Cuban invasion didn't happen was the S. African army being parked a couple of miles outside of Lobito Bay. I had a couple of acquaintances serving in the army at the time and they each said they were frustrated at having to watch the Cubans disembarking while the politicians did politician stuff. A common comment was "we could have destroyed them before they ever got ashore". After a while, they were withdrawn back into South West Africa (there was no Namibia then).
Given my experience of working with the S.A. defence forces (Navy), I honestly couldn't imagine the country actually developing either a nuclear weapon or the means to deliver one. One example of the native arms industry I witnessed at first hand was the attempts to develop a proximity fuze for use with anti-aircraft artillery. Using a pair of 4.5" shore mounted guns (identical to those mounted on the Type 12 frigates) a series of test shoots at an aircraft towed target took place. Tests resulted in failure after failure with the shells going bang at very low altitudes. Aircraft above 1,000ft were totally safe from this shell. Eventually someone back at the head shed figured it out; the radio frequency chosen for the fuze's operation was almost identical to the frequency of the local Cape Town Radio FM transmitter. Between the shore battery and the local FM radio station was a couple of hills, including Table Mountain. As the shell climbed from the gun toward the target, it reached a point where it rose above the shadow of the mountain, picked up the signals from the transmitter and went bang!