[Mike C]

Somewhere there is a law of diminishing returns to gear. For instance, my buddies '69 Firebird with a 2800 rpm converter at 3.42 ran 10.69 @ 123 going to 3.73 slowed it down and required more engine mods.

I think you will be most happy with the 4.10 and I know they are easier to find. The smaller displacement, usually the better they like more gear. If you get a 283, go for the 5.13! But with your combo, just get the 4.11. That is still a 20% increase over your 3.54.