The Racers Math Handbook & Car Craft mag have forumulas to figure boost for Roots Blowers based on Displacement of the Supercharger * % Over/Under Driven*25.58/Engine Displacement -14.7.

Looks like I need a 10-71 as at 1:1 on a 511 it creates 10.2 lbs of boost.

After attending Federated Auto Parts event at Summit I met afew Roots Blower affecionados and it seems a 480-511 Supercharged BBC Engine is a match for a N/A 496-565 CID BBC.

It seems like it would be easy to make 770-900 HP/ w or w/o Intercooler with a 10-71 but could a Tall Deck 427 Truck block take this abuse( Street&Drag)?