Turbo is the way to go to make big power. We made over 1200 hp with a "small" 94 MM turbo on a 331 Yates headed small block in a old Pro 5.0 car that I crew chiefed. That car was flat out brutal but compared to the technology today it now looks mild.
If you want to make big horsepower your going to have to really break open that piggy bank. It will require custom fabbed everything and large bills to buy the parts. As said EFI is the way to go but expect to shell out around $5000 for a good set up which will include ECM, wiring, sensors, injectors (about a $1000 just for them)and, a good intake drilled and plumbed for injectors. Then you need to fab up the intake tubes and the exhaust headers from high quality stainless, another $2000-$3000. Get a high quality intercooler, wastegate, blowoff valve (these depend upon your set up). Oh yeah the turbo...that will set you back about $3500 for a big boy. Before you even start building the engine you'll need to have at least $13000-$15000 to get the ball rolling for all the parts and fab work.
I could go on and on with parts list and dollar amounts. IMO there is no better power adder out there if you really want to go fast...just be prepared to spend some big $$$$
Dave Walters
427 Galaxie Registry
Website
http://home.ptd.net/~pwalters