clearly you aren't going to change cars so I won't touch the subject. I would personally invest the money in something that will be worth something later but I don't think thats the route you want to take, so.... I'd probably go with a 408 with a rather large turbo and set the car up with some nitrous for when its not feeling fast enough on the turbo. Build the motor as bad as possible, take no short cuts!! Make sure to replace all the suspension and you will have a amazingly fast 3rd gen that will really surprise the hell out of people on the street and at the strip. If you stay out of the throttle and away from boost it will probably get decent gas millage as well.
good luck with the project
good luck with the project