I had an 81 C20 that I converted to a 6.2L diesel turbo with a 700R4, 4.10 gears, and 31" tires. I felt it was the perfect combination for power and economy. Like mentioned above, the 700R4 has a steep overdrive, so it makes the 4.10 gears happy on the highway but still leaves you with the proper gearing for towing. I think sticking with your current combo is a good idea.
Casey
1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter