The exhaust manifolds will fit fine, and work pretty well on a 383. The flow potential is not a bad match for the smaller engine, and good pipes will answer for the rest of it. Also, the factory Hi-po manifolds are quieter than headers, and look really cool. What is your planned compression ratio? This will affect a lot of your other choices, and also affect your operating range and flow needs. The stock heads will limit you to about 400-450 BHP, but that's really a lot for a street car. Do you plan on using a high-stall torque convertor, if it's an automatic? Will the car have deep gears? Answers to these questions will help a lot in sorting out your combination. Expect to use a dual-plane intake, and a 750CFM carburetor.