This is, of course all just silly "what ifs", but I disagree that the game would be decided by GSW's back-court dominating. Ainge and DJ were both fantastic defenders. Sure, if we played by modern no-hand-check rules, they aren't going to shut the splash bros down. But they aren't going to let them go crazy. If they can't be checked, their own offense suddenly gets a kick. And if they play by 1986 rules ...
And Wedman and Sichting were also both great scorers off the bench.
To me, the question is who is going to slow down the scoring of Bird-McHale-Parrish. Green, Bogut, Barnes & Ezeli are good defenders, but they haven't played any modern front court like those three. All three of Bird-McHale-Parrish required either your best defender or a double-team to defend. Throw in Walton and it isn't really fair. McHale and Walton were foul-generating machines. They would be going to the free throw line constantly. Bird could score from anywhere on the floor.
Who do you put your best defender (Green) on? Bird? McHale & Parrish will eat up Bogut & Barnes.