A 550 hp 440 is mainly consider mild cause it can spin less than 6000 rpms to make it.
There both gonna need heads cam intake carb headers cr etc.. Are the spec gonna be all that crazily different from one another?
Couldn't do 550 hp 340 around 7500 rpm with like a set of Trickflows or similar and Roller cam and the appropriate accessories ? How much less cam and head flow would a 440 take to make 550 hp and how much less a 540 take over that? Not like at some point with enough cid you could make 550 hp with stock 440 top end parts.
Here's a Honda k24 2.7l making 519 hp @ 9400 rpm with 435 cfm per cylinder 1740 total cfm which would be 218 cfm per cylinder for a V8, yes it's a crazy high rpm engine but doesn't need a crazy amount more total head flow to do it. To me shows it is a somewhat similar in it's needs to make similar hp within it's variables, Aka similar recipe.