if the engine is near stock or a mild build an h pipe is fine . . x pipes are for big hp high rpm engines.

From a build point of view, the x pipe can cause some problems getting your transmission in and out if the need arises.  I had a heck of a time with mine and ended up reverting back to an H-pipe.

from joe sherman, lol.

"Dont waste your time and money== The x pipe or H pipe is for little weak suck 289 Fords ( whatever )"

Old addage "H" for long tubes, "X" for shortys.
I used; "X" on a stock EFI 5.0, mild 5.1, moderately warm EFI 331 stroker. They promoted drone on all three. Yet I still use "X's" cos I finally found a way to reduce the drone.

Tubo

If I can find the seller in Waco, I'll post a link. Essentially I miss ballanced one side with restrictors before & after the muffler on one side.
 Ford used different sized mufflers in the fox body and SN95 with 5.0 roller V-8's

Tubo

My last mustanf I had both a 2.5" H pipe and a 3" Dr. Gas X pipe on it at different times. The 2.5" H pipe with 2 chamber Flowmasters resulted in a slower revving and more muted exhast note that sounded like what you would expect from a mustang. The X pipe with 3 chamber Flowmasters was much raspier and sounded more like an airplane than a car. It also reved much faster and had much higher RPM powerband. The idle was much worse and it would barely run at 1200 rpm, while the H pipe would idle at 1000 rpm just fine.

I know the 2.5" to 3" made a difference on some of these aspects.  With either exhaust you couldn't talk to your passengers, so I left the 3" exhaust on there and only put the h pipe on for long road trips where I wanted to sleep to the sound of snoring and not ringing.

I can email you a  recording of each setup with all other variables the same...same engine, cam, headers, etc.

BobN