Warriner,
congrats on the father son build up, I wish I had had a cool dad to do that kinda stuff with!!
Amount of lift and wheel/tire sizes are really personalized choices, so it makes this question tough to answer.
I feel more stable in my 69 with 7" of lift than I do in my 73 with a three inch body lift.
This is partially because of the tire and wheel combinations that are on the trucks. The 69 has 15x8 wheels (3 3/4 backspace) with 35 12.5 semi agressive radial mud tires. The 73 has mild all terrain radials in a 33x9.5 mounted on 15x7 Do**e wheels (w/3 1/2 b.s)
I am not sure what you mean by "soft" flares... rubber edge moulding perhaps??
Go to the galleries, find my cruise night and look through the trucks you see there. Find a truck that you like the looks of and I will find out the lift and tire/ wheel combination for you.
You can then have your dealer test fit the same size tire and wheel on your truck and see if it suits your needs.
Oh and in response to your lift questions, all lift front coils will be stiffer than the stock coils, almost all aftermarket shocks are also stiffer than stock. You will find that the stiffer ride may make the truck more stable even though it is lifted.
What brand of lift were you looking at, if you can be a little more specific, I am sure that someone on the board has or has had that lift in one of their trucks in the past. Thay will probably be more than happy to share some info about it.