My buddy has a 493 built close to your build. He was running 4.10s with 28 in tires. Went to 3.73 to keep the rpms down at the stripe. Ran the same times.
That's been my experience with an iron head 440 too. I've had 4.30s, 4.11s and 3.91s in it, and the car doesn't care. No significant change in et or mph, just rpm at the lights. Gonna keep running the 3.91s.
My dumbass theory is that with the limits of a small block flowing head on a big block, rpm from steep gearing doesn't do much good.