The Aries performance muffler has low back pressure and is good for higher performance engines. I removed the baffles in a muffler thinking that it would make my engine run better but all it did was make the car loud. The Aries performance muffler worked just as well and has a low amount of noise. I also tried a header made from steel tubes and a straight pipe. It was not any better than the Aries muffler and the stock exhaust manifold.
A header and straight pipe would probably add performance in a racing engine, but for street flat head engines, even ones with high flow carburetors and high compression heads, the stock manifold and the Aries performance muffler is the best combination.
The Ford muffler and exhaust pipe was well engineered. The pipe leading into the muffler is larger than the one exiting the muffler. This is because the exhaust cools in the muffler so that the larger pipe at the exit is not needed. The muffler is tapered for the same reason.
If you want to make a bunch of noise, a cut out is a good option. That way you have a choice of noise or not.