Does anyone know of a Twin Screw supercharger that would fit on the 4.3L vortec eninge?

You won't find one that won't require extensive modification to the lower intake plenum. There aren't any bolt on kits for our application. Most either go with a turbo or a CSC.

CSC?

CSC == Centrifugal Super Charger. Paxton (http://www.paxtonauto.com/), Vortech (http://www.vortechsuperchargers.com/), ProCharger (http://www.procharger.com/) to name a few.

Gotcha.so many acronyms, so little knowledge...

rat on s10forum is building an Eaton M90 roots type set-up totally custom. i think that whipple used to have a twin screw for the TBI trucks if im not mistanken