Are 3.55 gears a good choice?

A cheaper alternative may be to bolt on a set of taller tires for longer trips.

You would be surprised how much tire diameter affects rpm.

A 30" tire may actually make the 3.91's much more highway friendly but still have the punch you need off the line.

They work well for me with this combo but I can cruise fairly comfy at 65 mph just shy of 3000 rpm.
If I get tired of the rooms I just back it down to 60 mph.

The 3.23s were so nice on the highway and not bad off the line but not impressive nor good for burnouts like the 3.91.