Oooh ooh! I can help with this one 
Nearly 2 years ago I bought my 2001 w/ 120K on it for $2350. It has been 19K miles, 28 autocross runs over 3 events, a gymkhana, a drift event, 3 track days/HPDE's, and 150+ 1/4 mile passes later I still like it.
Stay away from the 2000 and older models, they have the non-PI (Performance Improved) 4.6 which was rated at ~175HP? and plastic thermostat housings that blew out. They are also no cheaper.
2001-2002 are really hitting their sweet spot in pricing. They also have the PI 4.6 worth 239HP. A real P71 nets you the HD version of the 4R70W with a cooler, an aluminum driveshaft w/HD u-joints, quicker rack w/power steering cooler, oil cooler, 8.8" rear diff w/LSD (usually a 3.27), HD control arms and shocks, higher/stiffer springs, and 16x7 steelies. The brakes are freaking HUGE and a quick pad/rotor upgrade away from popping your eyeballs out of their sockets. The brakes are seriously the best part of the P71.
2003-present got a completely revised frame, suspension, and brakes. Power uprated to ~250ish? but the only difference is the intake tube and the tune. The suspension is better, but mostly in a packaging sense, and the steering became rack and pinion instead of recirculating ball. The brakes actually got lifted from the P71 of 03+ to make the brakes in the 05+ Mustang, so upgrades galore are available there. Otherwise, they are pretty much the same. On 03+ 17" wheels are the minimum and they use a FWD/05+ Mustang offset.
Of the two it's preference on what you want. Mustang take-offs are cheap and the r&p has better feel, which makes me want to upgrade to an 03+ one day, but the 01-02 is lighter with better handling and has sexier wheels. Either way you win in my book.
You can find an ex-patrol P71 for $2000-$3000 for a decent mileage nice one. Some will have holes (mine has 3 antennas and 1 hole) but if you're lucky you can find a "clean" one. Don't even bat an eyelash at the interior, all of the Grand Marquis and civvie Vic stuff bolts right in. I was able to find NOS in the box seats in the color I wanted in my hometown in less than a week. Carpet was $89 shipped new on eBay. All cars have the power seat harness tucked under the carpet/rubber so you can upgrade there as well.
Maintenance is cheap, insurance is ridiculously cheap, they are 5-star crash rated for the kiddos, and they have the good baby seat hooks. The trunk is big enough to park a Miata (we fit an entire FB interior in the trunk including the seats, headliner, and dash plus the P71's full size spare AND a driver's door for the 7 with no problems)! You can also fit an entire GSL-SE suspension in the trunk (including a complete rear axle, it's narrower than the trunk). Or a 302/AOD hooked together. Or two 17x9's w/255/45's, two 17x10's w/275/40's, and the 225/60/16 spare. It hold a LOT basically.
ANy other questions? 
