Tim Duncan had 19 points and six rebounds for the Spurs, who also had double-figure points contributions from Kawhi Leonard (16), Tiago Splitter (14), Tony Parker (13) and Danny Green (11).
The second-seeded Spurs will open the conference finals at home against Memphis on Sunday.
Elsewhere on Thursday, Carmelo Anthony's 28-point haul helped the New York Knicks stay alive in their Eastern Conference semi-final against the Indiana Pacers with an 85-75 victory in game five.
"We wasn't ready to go home yet," Anthony said.
"We wanted to protect our homecourt. We let one slip away here on our homecourt that put us in the position that we're in right now.. But we're just taking it one day at time, we have faith, we believe.
"And we feel confident about this one....We proved that we can win on the road. And we have to go to Indiana and do that."
Chris Copeland added 13 points from the bench at Madison Square Garden as the Knicks reduced the series deficit to 3-2.
Paul George had 23 points for the Pacers, who can close out the series at Bankers Life Fieldhouse on Saturday night.