10 sec. 318?

A couple notes: Roots type blowers (what you're talking about) are not easy on parts and the engine needs to be built to make the best use of them. You can run them underdriven to keep it together and make people smile but you won't make anbywhere near that power level. In fact, for the power level you are talking about you will nee a bit of work and support equipment to keep things together. Knowing this, build a mild 318 and plan on building another dedicated engine for the blower. I wouldnt advise anbything else.