A few months ago a empty "Z Back" K3 cab was on Boston area Craigslist for 50$... If I had room I would have scooped it myself!
Example shamelessly ripped from some guys photobucket
If you search with something like All of Craigslist you can decide just how far is too far in getting the cab style you desire.
I wouldn't expect to get anything free without some "bonus" features like water damage, warping, cracking of the MDF. If you want to invest the time in MDF repair, Bondo, a fresh spray of primer, sanding and final spray of topcoat go a long way.
oh no i dont expect free at all. Im just looking for someone local who has one. there is a place near by me that has tons of them but they wont let any go