Turbs, A 500CI older caddy motor would be a big iron block heavy beast that would weigh down the front end of most swaps beyond driveability. Not so sure that motor would even be able to fit in the engine bay... Not really a swapable motor for most applications...
Good point on all the adaptor parts for the LS1.. So then spend the 10 grand and get a new 5.7 tundra motor...
I would first try to get a used 4.7 tundra block motor and bust out the drill press and bore it to a 5.7 and then go from there...Get some nice flowing heads, and then save some cash for some other mods..With that you get pretty much the same motor...