Andy Ruiz is a hard puncher, look what he did to Anthony Joshua in the first fight. But Jerry Quarry was a tremendous counterpuncher, especially to the body, he did tend to cut but I think that in his prime, he outpoints Andy in a competitive contest.
Ruiz hand speed and short sharp combinations up close could make Quarry uncomfortable. This would not resemble Quarry's other fights with big hitters who tended to only throw 1-2 punches at a time and he'd have less time to plan out his counters. It would be a very long, rough, and exhausting fight for both men as they both had solid chins and would likely be duking it out up close smothering each other's punches. If quarry targets the body early that would give him the best chance since Ruiz huge belly is wide open, he can't miss it, and it would slow down the blubbery Mexican freight train in the Long run. Ruiz would need to pounce on Quarry early and bully him with his weight. Use smart educated pressure and keep his hands up to avoid getting clipped.
Pretty much how I would see the fight panning out, when I first saw this wasn't overly impressed with the " who wins " but on closer inspection a very interesting pairing, I can't quite define, or put into words but there is something about Jerry Quarry ( even the name ) that I like and feels me with a " Glow " am I going back to my youth ? keep well Richard.
What bothers me about Ruiz is he seems to throw the same basic combo over and over again... jab, cross, hook. It's fast and fluid but he doesn't show a lot of imagination. If Quarry didn't get stung the first few rounds, he would figure that out and counter the cr@p out of him. This would be a good tussle, a fan's fight.