Unless I'm just overlooking it, I don't see anything that definitively states or shows the rotors as being for the rear.
The one in the photo appears to be for the front since the sides of the hat taper inward toward the wheel mounting surface. A rear disc with an internal set of drum shoes for the parking brake would have a hat with parallel sides.
you have to click "More Info" and it will tell you, however i do have the parts numbers handy.
4000 series: left 42149SL, right 42149SR $119.95 each
4000XS series: left and right, 42149XS $130.95 each
Rusty, no they aren't exactly cheap, but they are vented rotors for the 98-02 Crown Vic, plus a complete Crown Vic setup from the junk yard, around $100 or so and the kit with the spacers for around $40, so for under $400 you get a rear disc setup with drilled and/or slotted VENTED rotors and a drum parking brake, doesn't sound too bad to me, hell even you had to replace the calipers it would still be under $500
so yeah, the rotors are a bit on the high side but overall you'd have a pretty darn inexpensive really nice rear disc setup. also, you wouldn't necessarily have to buy the rotors at the same time as the rest of system, really you could even try it out with just the solid rotors and upgrade to the vented ones later if you so choose.
BTW, i'm still not done looking yet either, i could swear i've seen some cheaper on ebay before but haven't been able to find them lately, it may be that they only put them on every so often or something