Stoltz played five times in the European Challenge Cup this season for Petrarca and also played in the Heineken Cup against Leinster and Gloucester for Agen in 2006/07. Mockford, meanwhile, is a former member of the London Irish Academy.
The Golden Lions moved head coach Eugene Eloff out of his position last week after a disappointing Super 14 season, but they are still expected to provide the Lions with a big challenge.
Back row man Cobus Grobbelaar will lead the side and assistant coach Rob Howley has already warned of the danger posed by No 8 Willem Alberts and scrum half Jano Vermaak to the tourists.
Springbok contender earl Rose, who played for the South African Training XV against a Namibian Invitation XV last week, is confined to the replacements bench as Coetzee opts for the experience of 31 times capped Andre Pretorius at No 10.
Former Springbok prop Lawrence Sephaka will be the cornerstone of the home eight and he will have Willie Wepener alongside him in the front row. Wepener is picked ahead of the Saracens bound Ethienne Reynecke, who is among the replacements.
Also among the replacements is USA Eagles international Todd Cleaver.
Xerox Golden Lions
Louis Ludik; Michael Killian, Jannie Boshoff, Doppies la Grange, Dusty Noble; Andre Pretorius, Jano Vermaak; Lawrence Sephaka, Willie Wepener, Gwert Muller, Brad Mockford, Willem Stoltz, Cobus Grobbelaar (captain), Franco van der Merwe. Willem Alberts
Replacements: Ethienne Reynecke, Janse van Rensburg, Ernst Joubert, Todd Cleaver, Chris Jonck, Walter Venter, Earl Rose