$6,000 into modifications to make power will lead to another $6,000 in making the rest of the drivetrain handle the power, folowed by $3,000 to make the chassis handle it. Then follow that up with another $6,000 once you have a strong drivetrain and the power you have isnt enough.
I would suggest a supercharger with 6-7psi and call it a day with money left over.