Chris Finch's men play Russia on the second day of competition, but it was feared that starting guard Lenzly, who tore his calf muscle in the prestigious exhibition match against the USA, would miss out.
Clark was struggling with an ankle sprain picked up against Tunisia in Team GB's final warm-up and both men were given the final week to prove their fitness, with a Friday deadline to make changes to the team list.
Chris Spice, Great Britain basketball team leader, said: "Thanks to some outstanding work by our medical team at our dedicated training base both Dan and Mike have been cleared to compete in the Olympics.
"Both players have worked tirelessly on their rehabilitation and should be congratulated on their efforts," he added.
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