He will cover starting hooker Matthew Rees of Wales, with Englishman Lee Mears dropped from the match-day 22 after starting last weekend's opener in Durban.
The Edinburgh man is likely to enter the fray during the second half with South Africa loading their bench with forwards and the Lions expected to try to counter that with fresh legs in the front row.
Should Ford come on he will be the first Scot to represent the Lions since Gordon Bulloch, coincidentally another hooker, played against New Zealand in the last Test four years ago.
His selection represents a whirlwind rise to the pinnacle of the British and Irish game after being left out of the original touring party, only to be called up after Jerry Flannery was injured.
Ford, who like Rees brings more bulk to the No.2 shirt, said: "It is a great honour to be representing Scotland in a Lions jersey in a Test match.
"I'm really looking forward to it. Hopefully I can do everyone proud if I do get onto the pitch and fly the flag for Scottish rugby."