Will I regret change to 3.55s from 2.76s

I have a 3.55 SG 3rd member for the 8 3/4 in my Duster (~400hp 360, 904, 27" tires), ran it for about a year and it was fun around town and at the drag strip but started to annoy me on the freeway. I put the 2.94 3rd member back in and prefer it this way because I like to be able to keep up with traffic and cruise at 75-80 mph to get where I wanna go. I won't be putting the 3.55s back in until I swap in a TKX 5-speed, at this point who knows when that will be so 2.94s it is.

In your case since you aren't cruising over 60 mph I think the 3.55s will be fine. I just got sick of it because I built my car more for high-speed cruising and handling than straight-line drag runs. With 1.14" torsion bars and 18" wheels my car starts to feel like it's "settling in" once above 70 mph or so and feels "in the zone" around 90 mph.