I would use a couple loaf pans for the body - use another loaf pan to make the legs, head & tail!
U could do it so its sitting down and the legs are lying down - Prop the head up with a dowel!
I also found this great dachshund cake!
http://cakecentral.com/cake-decorating-ftopic-682831-0-days0-orderasc-.html
I am making a shetland sheepdog cake in a week or so. I have looked high and I have looked low for a sheltie or a collie cake pan. Nothing! I can't draw to save my life, and I don't think I am ready to tackle a fancy 3D cake yet so I went online and bought a cheap (about $1.20) sheltie cookie cutter. I am just going to cut out shapes of shelties and maybe some bones for the cake with cookie cutters.
After you make your cake though I would love to see it. I have a friend that has a daschund, and I wouldn't mind trying a daschund cake. 
It also might be easier to use rice krispies for the head of the dog!
They do sell the scooby doo dog cake pan (maybe you could use that as a guideline!)
Good luck ladies!
Ladies,
I am also in need of making the dachsund cake. Please email me this document from the cut up cakes book that you mentioned at [email protected]
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