K, I had a really long post here and for some reason I must not have been logged in and it didnt let me post it so I'll summarize it. Build the small block turbo, the big block is likely too much in reality. Think of what you intend to do with this car and ask yourself if you 'need' that much. I know you likely 'want' it and I can guarantee that I want more power too but keep it within your limits. I personally have the same question raging in my head and as much as I hate to realize it the small block is where you should invest. You already have it, its lighter, parts are cheaper, you have other accessories and you can still make plenty (unoptimized can easily push 650 hp and torque) of hp and torque with a blown setup. I definately agree with hotwheels on the turbo issue, if you have ever driven in a turbo car there is nothing that will give you that seat of the pants rush when the boost comes in. I also have a love affair with turbos and believe they are well worth the money in gains and the long run. Its really not the turbo that costs, its the packaging. If I even get started on them this post will be three times the length it already is if not more so I'll just stop with them here. Superchargers are quicker, easier and cheaper to install in many cases but in reality do you need 1000 hp?
With all that moral stuff outta the way I'd say go with the blown BBC.
I am a new member to this sight and thought i would post a reply to the bbc dilema.I just sat a 427bbc with a vortec blow thru box in my 69 camaro.Kinda wished i would have put a turbo but i have had 5 superchargers in the past and thought i would stay with that.I also switched from sbc to bbc and kinda wished i wouldnt have (didnt realize the cost).Its in now and going to try to start it this weekend.I guess if i had to do it over i would have done the same thing again because it looks pretty cool in the car.