We made a chicken coop out of an old 1970 ford truck that my husband blew up the engine. We tore the engine out to take it to a mechanic to see if they could fix it. (some background, I am a mechanical engineer with an automotive background, hubby is a software programmer - but since I am the wife, he never believes me)
When we did pull the engine out (you WILL need a hoist - we used a block and tackle, some heavy duty rope and the joists in our garage) we started taking it apart, I saw a crack in the block, the crankshaft was BENT and 3 rods had been bent, and 2 piston domes were cracked. I didn't think it was worth a repair, easier to buy a working engine.
Actually, we discovered it cost just as much to buy another running 1970 ford pick up.
Som after it sat in the driveway, we eventually pulled the tranny out, too. Well, more like we supported it with a jack, unhooked all remaining connections, dropped it to the ground, and pulled the truck away from it.
By NOT having ANY motor parts left in the truck (and draining the gas tank) we didn't have to worry about any residual fluids leaking onto our land. It provided us a truly mobile coop - we have to pull it with our other truck. But with the engine and tranny out, and the hood off, if it is sitting on flat ground, my husband and I can actually push it. But having automotive tires on it, it can move over bumps and ditches in our land, that the tires on our other coop couldn't do.
You can do it. We plan on taking the front panels off, and building another coop section on top of the front of the frame. Right now, we use the cab for feed storage, and I still use it to steer it when we move it across the pasture.
YOu can do this, but you will need a way to hoist out the engine, it is too heavy for people to lift out of the compartment.
Here are pictures of our coop built on an old truck
http://kristinandlarry.blogspot.com/2010/11/chicken-house.html
Here are pictures of our first mobile coop, this is before we build the doors and nesting boxes, so we could push it ourselves. Once we finished it, it had to be towed by a truck, and would still get stuck in the mud. After two years, it started to fall apart, and is now a sheep scratching post.
http://kristinandlarry.blogspot.com/2007/08/chickens-are-big-puppies-are-fun-and.html