Did I hear my name?
You don't have to actively out there buying parts to have an interest. I spent an eternity researching different parts and combinations before I spent a cent. I'm sure a lot of people were surprised when I stopped just talking about parts, and actually started buying them!
I don't know of anyone in the world that sells a cast alloy intake for running 8 throttle bodies on an LS1. Having said that, a friend of mine gets the most incredible looking sheetmetal intakes made for all his customer's engines. These things are better than artwork - stunning quality inside and out. I don't have any pictures, but he'd end up making something like this :
The actual throttle bodies are widely available.
If you went with this type of manifold, you'd have to run a modified / custom engine management system. I like Motec, but
http://www.carputing.com/ could probably do the job for you.
Another guy with a sheetmetal SINGLE throttle body is making big horsepower at
http://www.ls1speed.com/som.cfm .
Nothing beats the look of those throttle bodies standing proud though....