For lower speed stuff and 4x4 low range they'd all be fine but to keep up with traffic these days you'd definitely want a 5.3L or 6.0L with a turbo and some good brakes as well.

The only way I'd ever use a 4.3L v6 in a 2500 series is if it had a turbocharger. The 3.8L engines with a factory supercharger are good swaps for smaller stuff like jeeps but for a 2500 series suburban that is essentially a brick when it comes to aerodynamics, like you mentioned, you're going to want somewhere around 300rwhp and 350ftlbs of torque if not more these days.

It's easier to find an LS now than a 4.3L v6 anyways so I don't know why you would go out of your way to swap a v6 into a vehicle where the smallest engine was a 350 unless you already had one that was bored and stroked and had a turbo or something.