Yes there's many factors, but there's a general range of hp people get that you can ballpark it somewhat. Never said these are a 100 % comparable just similar enough to kind of see what good heads would do on 5.9l that's in a similar ballpark.
To me displacement is dynamic, eg. at the same VE% a 440 @ 5,000 rpm and a 360 @ 6,111 rpm are basically the same size cause they both should be displacing the same amount of air around 637 cfm which should have similar hp capabilities at least at that rpm. So at those rpms they would have a displacement of 637 cfm. So unless the 440 has terrible VE% and the 360 has crazy stellar VE% I doubt they will displace (flow) the same at same rpm.