I have gone through my Afrikaans language sources once again - SADF had Buffel troop carriers, Ratels (inclusing the 90mm tank killers), Eland armoured cars (including the 90mm tank killers), artilery and MLRS (like your Katyushas). No centurion/olifant tanks were deployed.
The Soviet T34/85 and T55 tanks were knocked out by 90mm armed Ratels and Elands.
http://www.sadf.info/SWATF%20Operations.html
This is an English source - Read the bit about Operation Hooper - it states that it was during Op Hooper that olifant mbt's were deployed for the first time.
Regarding the 96 Centurion tanks - thats propaganda my friend. To be honest, many of the FAPLA and SWAPO soldiers were illiterate and uneducated. Anthing with a turret and a barrel was seen as a 'tank'.
Just to make sure however I phoned a friend of mine this morning. He took part in Operation Protea serving in 61 Mechanised - they were one of the units that took part in a lot of the fighting. According to him there were no olifant mbt's in their battlegroup and to his knowledge also none in the other groups.
The SADF strategy at this time was to move into Angola as fast as possible, hit hard and then get out as fast as possible. Tanks did not fit into this style of warfare and therefore they were not used during this period of the war.
Another point: the SADF had encountered Soviet tanks before on operations in Angola. Fortunately these tanks were dug in on many occasions and were not used in a mobile role. If these Soviet tanks had been used more agressively the SADF would have had to deploy tanks to counter them. When we did run accros dug in tanks they were easy to take out using Eland armoured cars and Ratels as some of these units were armed with 90mm guns.