Haven't done this yet, but have read a lot on it - take what I say with a grain of salt (though I know Chevys well enough).

Your stock tank has baffles, so it's good to go and so are your fuel lines. Going to need a stronger in-tank fuel pump - you need about 50-60PSI. You'll need to harvest both your stock wire harness as well as parts form the ls donor - might need to harvest some of your old engine sensors too to make stock gauges work right. Plenty of hood space for the swap, but your chassis might rub against the exhaust manifolds - especially on the passenger side. Might need to grind the frame a bit or switch headers/manifolds. LS AC will not fit the chassis unless you do some serious cutting, so if you want AC, you'll need an aftermarket kit that moves it up to the top passenger side of the motor - doing so might screw with the stock ls air intake (could have to get a cold air intake kit). Will need to reflash the pcm/tcm. Engine should be drive-by-cable, so you're stock accelerator cable should hook right up to the throttle body. 700r4 will bolt up to ls but needs a few mods - mostly enlarging the holes on the flywheel. I think you should be able to retain your cruise control too. Can't do that with genIV.

Hope that helps. I'm sure there are others here who know way more about this than me.