I need a gear change in my Duster and just 3 days ago had a new best of 1.49 60' and a 10.95 ET. Problem is that it hits the rev limit (7k) in 3rd around 1000'

I wonder how much 60' I will give up going from 4.86 to 4.56 gears? This is a 3.58 stroke 374 inch engine. Any guesses or personal experiences?

Yeah, it's got a smallblock.