For headers, go with a quality set intended for a third-generation F-car. The exhaust flange for the original TPI heads, the '78 castings, or the Vortec units should be the same, so that shouldn't have any bearing on your choice. However, avoid going with typical universal full-length tubes, even if smog checks aren't a concern for you. The third-gen cars have precious little space under the hood, and even less under the car, so even the full-lengths that fit the engine bay will cause you headaches when it comes time to make up an exhaust system. A good set of shorties with matching high-flow Y-pipe can support plenty of power for the type of combination you're planning. Back it up with a big-diameter single-tube after-cat system and the engine will breathe easy, plus you won't be dragging the exhaust over every imperfection on the road. Edelbrock, SLP, and Hedman all offer tubular shorty-style headers and Y-pipes for your car.