Centre Ringrose and back-row Van der Flier have both recovered from hamstring strains ahead of Saturday's Dublin meeting with the world champions after missing the 46-19 win over Australia at the weekend.
McCloskey misses out with a recurrence of a groin injury that forced him to retire hurt in the first half against the Wallabies. Bundee Aki was introduced as his replacement in midfield.
Leinster prop Thomas Clarkson has cleared all head injury assessment protocols and is set to train fully.
Ireland lost against New Zealand in Chicago on November 1st before bouncing back to beat Japan and Australia.
Saturday's South Africa match is their final game of the Autumn Nations Series.