I'd really like to see someone do this swap. Whether it's a 5.3L or an LS1, as long as it's a NBS and the swap is a v6 to a v8.
Let's see. You'll need another PCM, one from a '00 truck will work, that had a v8.
I'm not sure , but engine mounts and a v8 harness. I'm not sure if it will plug into your existing firewall and body harness , but I don't see why not.
As far as the engine, nothing will swap over, like said above, but you can get a complete one pretty cheap.

keep us updated, seeing how much you have in your truck, from the pic, i'd say it's worth it,

good luck,

allen