The geometry and relative dimen-sions for the X stampings are the same whether used internally (perforated) or externally (solid). The basic design/tuning is that good.
   A final bonus for this MagnaFlow system (PN 15815 for '64.5-'66 V8 Mustangs, use PN 15816 for similar '67-'70 models) is it's flexability. It allows three possible exhaust outlet options. The simplest and least rest-rictive is to just install the provided turndown tips (poished stainless, of course) right on the outlets of the mufflers. This will simply dump the exhaust under the vehicle, before the

axle. The tips can be rotated outward to try to aim the exhaust out from under the car, but the benefit will be minimal, especially while sitting still. If you choose this option you need to make sure your underbody is fully sealed to prevent exhaust fumes from getting into the interior. You'll also have to be willing to accept a higher noise level inside the vehicle since the ten-dency for the floorpan to resonate with the reflected exhaust pulses will be much greater. Fine for a racer or show car, not so good for a daily driver.
   The second option is the one most

people will likely choose: bring the pipes over the axle and allow the exhaust to exit just before the rear valance. The turndown tips will still be used, but now the exhaust will be better directed away from the vehicle so the chances of any leaking into the interior will be minimized. Similarly, resonances will be virtually elminated since the exhaust pulses will also be pointed away from the floorpan. The last option is to bring the exhaust tips through the rear valence as was originally done by the factory with many of these vehicles.