Llewellyn, who made his first appearance for his country against New Zealand in 1989, also claims the Welsh appearance record with his 88th cap taking him one ahead of all time greatest points scorer Neil Jenkins.
And the 35-year-old second rower is joined by new cap 33-year-old back row Jason Forster in a forward pack which will be duly tested against the might of the Pumas.
But it is in the back division that coach Mike Ruddock has made his two enforced changes, one positional, from the side that beat the Barbarians 42 - 0 in the uncapped match at Bristol's Ashton Gate.
Rhys Williams reverts to full-back in the absence of Wales' record try scorer Gareth Thomas, who hasn't made the three match Tour to Argentina and South Africa due to an ankle injury.
That gives Hal Luscombe the chance to impress on the wing in place of Williams, with the Dragon's utility back making only his second appearance in a Wales shirt.
WALES: Rhys Williams, Hal Luscombe, Sonny Parker, Gavin Henson, Shane Williams; Ceri Sweeney, Dwayne Peel; Duncan Jones, Mefin Davies, Adam Jones, Brent Cockbain, Gareth Llewellyn, Colin Charvis (C), Jason Forster, Michael Owen
Replacements: Huw Bennett, Gethin Jenkins, Darren Morris, Jonathan Thomas, Michael Phillips, Nicky Robinson, Tom Shanklin