I just bought an '08 cts for triple your wish list price. Manual versions are almost impossible to find, fyi. But the dual vvt 3.6 v6 is awesome! Peak torque @ 3100rpm for this application, tons of fun to drive.
As stated, ive seen crown vic conversions as well as older impala/ buick roadmaster manual conversions.
If you are interested in conversions, I am a bit partial because of my last car, but the dodge intrepid/300m/concorde/lhs would be a good candidate. Can be bought for around $2000 for a good one. Add a 6speed manual, drive shaft, and rear end, you could easily do it for 5k.
http://ecomodder.com/forum/em-fuel-l...vehicleid=6320