Just my $.02. I have installed dual exhaust on both my 67 Imp and 69 300 both with 440's. The 300 was done first and was the first modification done. I used 2 1/2" on both. The price between 2 1/4 and 2 1/2 is minimal. I think that 2 1/2 is a little restrictive even for a stock 440, of course its just my opinion and is much better than just a single exhaust. I will be installing 2 3/4" on the Imp some time next year. I like mine a little loud, so I use smaller size muffs. If you utilize the space given on an Imp for muffler size, you can actually keep them quiet with 2 1/2" pipes and large mufflers. The larger the muffler, the quieter it will be. I read an article in a mopar mag last month about exhaust. They did some dyno tests and came to the conclusion that you can run one size smaller tail pipes than what comes into the mufflers with no loss of horsepower. They were running 2 1/2" from the manifold to the muffler, then used the largest muffler as would fit, then used 2 1/4 out to the rear. One thing to check is the pipe diameter inside the mufflers. Most cheap mufflers neck down as soon as the pipe enters the muffler case. Some 2 1/2" inlet/outlet mufflers are actually 2" thru pipes. This will make a smaller muffler quieter, but restricts flow. Brian www.dusted74.com > HI all; One thing I have not seen mentioned in this discussion is balance. I > refer to the intake side of the engine. The original air cleaner on my > Imperial had one very small opening about the size of a quarter. It has a > single 2 in. exhaust. It seams very restrictive to me. When changes are made > to one part of a system, you should consider the effects on other areas. I > use an open element air cleaner on my car and should have improved the > exhaust system at the same time. Time, weather, and $ prevented doing > everything at once, so I will be putting dual 2.25 pipes and the new 50 > series flowmaster mufflers on when I can. I will use a crossover pipe (maybe > an x system) if I can fit it in. > Just my $.02 > Larry > 67Crown 4DRHT > >