26" tire and 3:23's is 2700 @ 65 for me witn a 904 auto. Going to a 28" should put that around 2400 with 3.23's I would think. 3.55 just a little higher. That's not too high for the highway, unless you want to cruise 80
How tall is that 275 tire with weight on it? Could use an rpm calculator and figure out what gear would suit you best for cruise rpm on the highway but also let it accelerate as well