Not a bunch of hills. Certainly not any long ones down here. Whenever I think I might downshift, I manually shift out of overdrive instead of possibly lugging with a big load behind me. Then I just pop it back in OD on the way down.
I also had a 97 suburban 3/4 ton with a vortec 5.7 the 4l80 and 4.10 gears. I still used the 85 suburbanto haul the boat, but I think that is because the 400 small block is a towing masterpiece (if you have a giant radiator).
With your stock 350 and short 4.10 rear gears, I think the 700r4 would be acceptable. You would need to have it built with quality parts. The turbo 400 will be bullet proof in your application. You could change to 3.42 gears, but that would add some expense. None of these ideas are real cheap.
Before purchasing the suburban I used an 87 1/2 ton 4x4 with a 305 sbc, 3.08 gears and a turbo 400. It didn't like the hills too much, but it pulled my boat just fine.
Do you just want to get rid of your SM465? Ever thought of a gear splitter? The concept is similar to that of a 2 speed rear, when you begine to climb the hill, you shift into 3rd high (4 low) allowing you to maintain stay in your power band without revving too high.
