That can was already opened, you're just now realizing it! Fortunately, it's not a lot of worms and you can easily put them back and fix it so that it doesn't open again. If you don't beat on your Tahoe and the lift and tires is more for looks and light off-roading, get the appropriate gearing for those tires (unless there's a good chance you'll be downsizing, then gear for those). Then you'd be fine with a mildly-built trans that just addresses the 4L60's common failure points. Having proper gearing will make the vehicle feel like it's stock to the trans. It's cheaper to get proper gears than to build up a trans to stand up to all the extra load. For the converter, you'll have to ask each converter manufacturer what they recommend. They'll build it based on your vehicle's weight, tire size, gear ratios, intended use, etc. You really just needed guidance on what converter manufacturers to look to, and you've gotten that.
