Just read an advertisement tid bit from JEGs suggesting that an H improves Low RPM HP while an X favors high RPM HP. With that said, I have heard that by reading the heat signature (spray paint, crayon or silmilar) on the exhast pipes between headers or exh manifold and mufflers for hottest area at the RPM range you decide to run for a short cruise will tell you where to put the X or H. Truth or fiction? Actually been there done that etc. info is what I'm looking for. I've already got my and friueds speculations which as always aren't all inagreement. Based on present info, probably looking to add an H to 300 with Offy DP/ Holley 390 with long tube headers. Might as well max the low RPM HP, since it doesn't make high RPM HP. I'm thinking I'll do the cruise heat signature at 50-60 MPH. This in turn should also assist cruise efficiency once the ingition/carb/exhaust are tuned as a system. I'm building my exhaust with same lengths from front and rear collectors to respective mufflers, rather than side by side mufflers with equal length tail pipes but unequal header to muffler lengths. The H will obviously be a little odd due to the 13 inch offset from front to rear collectors. Hoping the exhaust tone/tune is acceptable. If not, plasma, mig and relocated hangers. After all, it's a hobby., They are supposed to cost $$$. Data, facts, actually did the heat signature or staggered H like I'm suggesting.

 

Both setups are used to equalize exhaust flow and balance the sound. Thy are intended to compensate and restore some of the torque that is lost by running true duals. The other solution is simple, don't run true duals, a properly sized single will flow just as much air, but give more low end torque, a smooth balanced sound, and if combined with a dual outlet muffler, can still give the look of true duals (and much of the sound), without any of the disadvantages.