You could ask around on this site. There is some great stuff on there, and many people with private collection.
I have shoebox full of cassettes from the 1984 and 1985 seasons. Sometimes full games, but more often Paul Carey's post-game with highlights. Or JP McCarthy's highlights the next morning when he'd often interview Sparky Anderson. Or Eli Zaret giving morning recaps on WRIF, with JJ & the Morning Crew chiming in. One of these days I'll get around to organizing it and making it available somehow. I have something for just about every one of the 162 games in 1984, even if just a few minutes of highlights.
As for Opening Day 1985, I didn't attend but remember how festive it was. People fully expected the Tigers to repeat in 1985 and they did get off to a good start. I have a couple of hours of pre-game coverage (radio) but again, I need to get around to digitalizing it.