Swapping in an LS motor doesnt have to be a week long project as long as you're prepared. It has been done in a weekend, key is doing your homework and having all necessary tools and parts.
I had thought about doing a BB swap, I agree seeing a BB under the hood would be sick but think of how much they wiegh. Our trucks are slugs as they are, an aluminum LS based motor is roughly 90lbs lighter than a iron block, probably twice that of a iron BB.
With quality parts you can make twice the HP of any SBC or BBC easy. This build keeps coming to my mind "bone stock iron 5.3 with single turbo making 650hp, with room for more". I know for a fact I cant make anywhere near that with my SBC, even being built. If so, I'd need a new rotating assembly along with an aftermarket intake manifold. Cost = not worth it. Thats why I'm going LS based.
Its just not worth dropping in old technology when new tech is at your fingertips for far less.