Consensus when this topic came up before is that the stock manifold into the twin downpipe is as good or better than the IPD headers, as an example. Further, if available for your car, you can try the twin dp manifold with the Simon's 2" sport exhaust. I just put one in my '62 Amazon (this car had a B20 w/twin manifold already). Some issues with clearance, but I'm working on it and it's not a big enough problem to pack it up and ship it back. Sounds good and looks COOL, IMHO. Good Luck.