Tripucka and Manning had a conversation Tuesday about the uniform number, which was retired by the Broncos after Tripucka's career ended in 1963, The Post reported.
"It's perfectly OK for him to go ahead and use it," Tripucka told the newspaper last week. "I would be honored to have him wear it."
Tripucka added: "It's been retired for 50 years. That's long enough."
Tripucka was the first quarterback to ever play for the Broncos. He threw for a league-leading 3,038 yards in the franchise's first season in 1960. Only two other numbers (No. 7, worn by John Elway, and No. 44, worn by Floyd Little) have been retired by the Broncos.
Manning has worn No. 18 throughout his entire 14-year career.
The Associated Press contributed to this report.