From their website, the fuel rails are for the 96 - 00 Mustang...you've got an 01. Are you sure you need to swap fuel rails?
If you don't swap fuel rails, you need to tap into the schrader valve on the pass side fuel rail.
Here are a couple pics of my old setup on my (nitrous injected) 02 GT.
I mounted the fuel pressure sender on the shock tower, per Autometer's recommendation, to minimize and isolate it from engine vibration. I made a simple mounting bracket from a scrap piece of aluminum and a hose clamp. I drilled mounting holes in the top and bottom of the aluminum plate, and then cut 2 slots for the hose clamp to feed through. I also added a piece of high density foam to further isolate it from vibration. I epoxyed 2 washers to the back side of the plate to provide space for the hose clamp - essentially, the washers act as standoffs or spacers.
My setup had provisions for a fuel pressure safety switch and it also fed the nitrous setup, so I had an array of adapters, couplers and Tees. For just the fuel pressure sender, you'd just need the brass adapter that fits into the Ford fuel rail, then a male to male coupler, a short length of -4 braided line, then a couple other adapters/couplers at the sending unit end. I've still got these parts, although the Black GT is gone. Let me know if you need more specific info, part numbers, sizes, etc.
