From the men listed ,in their prime? Jack Dempsey Rocky Marciano Sonny Liston Floyd Patterson Jersey Joe Walcott Ezzard Charles Archie Moore (heavyweight)
Liston. Liston has the longest reach of the lot. While 84 inches might be a slight exaggeration, he likely had 82 inches in reach. This makes it very hard for fighters to escape him. Liston is the biggest puncher of the lot. Perhaps Rocky or Dempsey hit harder P4P but in terms of actual power, i think Liston having an extra 20 lbs on his frame gives him a bit more power. Liston matches well vs most 70s fighters. Punchers like Lyle and Shavers do not have the durability to hang in with Liston. Quarry doesn't have the long arms to stay away and gets cut too easy. Bugner is too passive to beat him. Frazier can be competitive but he would run into major issues with Liston's hooks and uppercuts. Liston would probably be 50-50 vs 70s Ali. Without Ali's lightning quick feet to stay away from Liston, Liston will be able to land a lot more. After Liston, it would be Dempsey and then Marciano. 1. Liston 2. Dempsey 3. Marciano 4. Charles 5. Walcott 6. Patterson 7. Moore
Charles and Jersey would have a few scalps too ,along with Moore but I don't see them grabbing the title at any time.
Liston is the only one on that list who would see any consistency. Some of the rest might produce a flash in the pan result and lose more over the longer run.
I could see those 3 beating Shavers,Lyle, Quarry, maybe Norton (big maybe but it's a winnable fight), Ellis, Young and Spencer. They might be able to get a post Thrilla in Manila Ali. All 3 would give spirited efforts against Frazier, but I think would fall short. Walcott and Moore might be able to score a knockdown but that's it. I think Foreman would be too strong and would catch up with them. But on the off chance they can get past the early Foreman onslaught and get him late into the fight, they might be able to stop Foreman. But Charles, Moore or Walcott would have to use every bit of slickness and elusiveness they can muster in this fight. I give all 3 the least chance against a 70-75 Ali. I think Charles would do the best and on an off Ali night, might pull off the decision upset