Alan - new register out so here is SMJ
ZS-SMJ c/n23500 BOEING AIRCRAFT COMPANY 737-3YO SAFAIR OPERATIONS (PTY) LTD
Reportedly due to be operated by Safair's offshoot Imperial Air Cargo.
Worth noting too, that the SA CAA have got the series wrong - it's not a 737-3Y
O (Yankee Oscar), but a 737-3Y
0 (Yankee Zero - GECAS's Boeing customer code). It used to be a 737-3Y0(QC) but it has long since carried its last passengers and now it's a 737-3Y0F dedicated freighter.
By the way, Chris, did that airports file I pointed you towards have everything you need ? It looked like it would fit the bill perfectly, but don't be afraid to say if it didn't.