If you're aiming for a Truck or Crawler mounted Unit, you might want to change how you watch ebay. The parts cabs come up fairly often usually without some combination of a boom, drive chassis, and engine cover. Bumps a $200 toy to more like $30, and may help with shipping.
Let me know what other pictures and measurements you may need.
Probably seen it already, but Factory model vs Toy
http://www.constructioncollector.com...rial-Unit.html
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Since starting the project, i've had a couple people question if it was really done back then, so let's watch some vintage Dragline loading Dumptruck action
https://youtu.be/Bu07huOng60