Like kstrong said, Accucraft (AMS) is coming out with some log cars very soon, and the pricing actually isn't too bad considering trucks and couplers are included. Best prices I have found so far are at http://www.rctrains.com/Rolling_stock%20AMS.htm. I am not associated with them in any way - I just googled it.
I may have to save up and buy a few of them short ones...
Scott
They take some time to make but Hartford Products makes several kits for logging cars in 1:20. Check out their site at
http://www.hartfordpr.com/
If you are running tight radius curves, you may want to call and see what size curves each kit can handle.
I've got a train of these for my Shay.
http://1stclass.mylargescale.com/JoeJohnson/Log%20Car/WholeCar.jpg
Both Bachmann and AMS make 1:20.3 scale rolling stock that matches their Shay. If you're into kit building, you can also get suitable rolling stock from Northeast Narrow Gauge in Wiscasset, Maine.
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