Brainstormin' 440 vs 5.9 ...

Well, yeah, an RV 440 without a cam change will quit well shy of 5000. Maybe shy of 4000! The 390 hp 440 Sixpack horsepower was at a rated 4700.
Maybe you could try some 15x33s?
I can just throw 3.23's in it. RV 440 should love them... but I'll try the 4.30's first and a quick cruise will let me know