Unless you can find a used one, just getting it rebuilt is the "cheapest" option.
When I got mine done, I also got a slightly higher stall put in it (2500 I believe. Isn't stock 2200?) a shift kit, new cooler lines and the rebuild.
Cost a little over $1300 all said and done.
1995 Mustang GT vert: AODE, 2.73 gears, O/R xpipe flowtech mufflers , 410,000~ miles.
2007 Mustang GT: 4.6, 5-speed, 3.55 gears, black on black. (dads car)