One HP per cubic inch with the 250 is not impossible, just difficult and very expensive. You can forget about using that HP figure and "daily driver" in the same paragraph. Very high compression, a roller cam, major cylinder head modifications, and a pretty exotic fuel system such as three side draft Weber carbs or fuel injection will be pretty much required, as well as split headers and dual exhausts, and a redline RPM of 6,000 or more. Bring a wheelbarrow for the dollars!
Jerry
