You can't find this on the Web.
I would suggest buying as many older matches as you can & just jot down stats when they flash on-screen. Otherwise there is no way to find this stuff out, maybe look up the NY Times from the 80s/90s the day after the US Open finals.
I have a ton of matches, magazines, newspapers over the years that have match stats buried away in them, too bad no one has bothered tracking them(the atp really is a weak source, even their recent updated archive doens't include winners, errors)
here are the stats from the '84 Wimbledon final: