That is a tough question. Under the rules as they existed at the time, the 1976 team was awesome. though if you could transport them to today's game, they had no outside shooters other then Ricky Brown. Leon Douglas, T R Dunn and Reginald King all had fairly long NBA careers. Ricky Brown turned down the NBA and played for the Globetrotters for a good many years, but I have no doubt he could have succeeded in the NBA. Anthony Murray was an outstanding ball handler and tremendous on the ball defender, but he had no touch whatever on offense. There is no doubt in my mind that this team was our greatest defensive team ever.
IMO, if they played the 87 team, it would depend on whether there was a three point shot or not. If not, the 76 team had so much inside power that they would have beaten the 87 team soundly. Under the three point rule, though, the advantage would tilt to the 87 team.
Just as footnote, since I am probably the only poster to see them play, the 1955-56 Ricket 8, which went 22-4 and 14-0 in the SEC was a pretty spiffy club in its own right. They were the first team ever to hang 100 on Kentucky, and had two stars who would have been good in any era: deadly outside shooter George Linn, and center Jerry Harper (who still holds many Alabama season and career records in scoring and rebounding).