727. Bop Air only flew the 200, so my even lower probability guess is 727-200 if SunAir was the successor to Bop Air. There seem to have been a lot of airlines called Sun Air, SunAIr or Sun-Air.
727-200 SunAir the first iteration. This was JNB-CPT in December 1997. My lady asked about a visit and they were great - even more so when they learnt that her late father flew Spitfires!