I ran 4.56, 4.11, and 3.91 in my 440 62, and with the lousy heads I'm using, the extra rpm from the steeper gears only wear out the engine sooner. I saw no change in E.T or mph for any gear change. I also noticed there was no need to spin it to 6500, or even 6200, it runs the same shifted at 5900.
My Tina started out with 5.57s, ((14x32 tires, and a glide/brake) changed to 4.57, it was quicker and faster (n/a small block)
My Opel has 3.50s. When I get the 496 or 540 in it, I'll probably keep the gear. Meantime, with a 454, I'm planning on .3.90s