please help

hi ive just bought a 91 caprice on the title it says police it has a blown 350 in it. I want to put another motor in it but i want it to have about 350+ horse power i having trubble trying to get any answers from any body about what i can and cant put in there that will bolt right back in and work with my computer i dont know much about these cars but i like it and i would like to play with some hondas and mustangs on the street any info would be good thanx.