If a certain other V6 owner doesn't go through with his plans, I know of a great idea for you to get to that number.
If he does, then I Would go with a centri style like the vortech. You'll just want to make sure your forge the internals or you'll be picking rod pieces out of your oil pan later. I don't see why you couldn't get to the 300ish mark with a centri with decent boost.
Now, the main question I have is....if you are going to be babying it for the most part, then why spend the money on the blower? That will be a lot of bank just to say you have a certain dyno number and the bolt on....
And yes, Back Yard Customs does do blower installs....rotating assemblies I'm not sure of right this second, but we will be expanding there soon once I find me a nice priced 351 or 460 block.