Even though I like the SBC for this one I'd go with the big block. You can get a crate 454 that will make 450 hp easily. You can even get a crate 502 for a little more. A 427 SBC will be in the same game as far as cost as the big block at this hp level.
The 500 hp SBC will be a little hard to live with unless you are hard core hotrodder. Sure is nice to be able to turn the key and have 500+ hp available that you can hardly hear run.
Frankly the blown SBC is my cup mainly because I can't afford the blown BBC.