The September edition of Car Craft has an article where they bought a couple eBay turbos and a surprisingly cheap pair of generic-fit stainless steel turbo headers (~$100). This formed the basis for an el Cheapo dual turbo SBC that was in a '55 Chevy shoebox gasser style drag car.
The results were less than spectacular but it DID run (7.20's @ 90 mph in the 1/8 or about 11.4 in the 1/4), and WAS cheap. By the end, it made about 600 RWHP on a dyno and cost less than $2K. Be aware though- little items like a Quick Fuel 850 CFM carb was simply "pulled from the CC carb pile"- so the actual cost is obviously a LOT higher than the number they quote. And the long block wasn't included, either.
Before you get too excited, this only begins to tell the whole story, so I'd suggest you do some serious research before going out and buying a pair of T3/T4 hybrid internal wastegate turbos.