2000 Cobra
2002 Z28
but the fastest for the money will be a 5.0 mustang and mod the hell out of it, like someone suggested. Then you also have the reliability of a 302 under your hood. if you find a good body with a blown motor, a 351W with forged internals will not let you down
add a healthy cam and you can leave it like that, or make it into a twin turbo, supercharged or nitroused setup with plenty of cash left over 
2002 Z28
but the fastest for the money will be a 5.0 mustang and mod the hell out of it, like someone suggested. Then you also have the reliability of a 302 under your hood. if you find a good body with a blown motor, a 351W with forged internals will not let you down
