Hello Tome, I have spent the last month learning about plows so I now am a expert!! Not really, but I do know a lot about this plow in terms of parts, availability, etc. I have one just like yours ( I think) but in the Ford version and it's a two bottom. Ford made these and also had them made under the Dearborn and Pittsburg label, but they are the same plow. If you could post a picture or drop me an e-mail picture, I could be sure. It would be helpful if you could take close-ups of the "wear parts" or those parts designed to be replaced periodically due to wear. If these were not maintained when worn, the plow could have been damaged, as mine was. The wear parts are the plowshares (the lower blade that cuts), the shin (the vertical crescent shaped cutting edge), the moldboards (the large wing), and the landsides (the flat piece of steel on the back side that slides along parallel to direction of travel) They come in two sizes, the rear one is longer, about 21". Lastly is the rolling landside, the wheel or dish on the rear. Depending on the condition of the plow, some or all of these may need replacement. These are all attached to the frog, which is the heavy inner structure that holds these in place. You don't want to damage or wear into your frog by using overworn parts. You may have a hard time seeing each part individually, as dirt can pack in and obscure the borders of each. Post some pictures of these wear parts if possible to determine their status. Shares wear first, so replacing them is easy. Landsides and shins are harder to come by, but can be found with effort. Moldboards are the least likely to be trashed, are available but more costly. Determine what needs to be replaced and if the bolts are fused with rust, don't even bother to try to salvage. Just get a sidegrinder and cut off the nuts from the back and use a punch to pop out the bolt head. New bolts are cheap and readily available. Replacing all wear parts on one bottom will cost up to $200, half of which is the moldboards which hopefully are still good
As far as the size and numbers of bottoms, these plows were sort of modular, in that you could add bottoms or change the size relatively easily by adding different diagonal frame members, and assembling it differently. Measure between the main beams (center to center) to determine the size.
Accessories were also available, such as coulters (cutting wheels in front of the plowshare) trash boards (small wings above the moldboards) etc. etc.
Manuals are easily available. I bought an original one on E-Bay. You are welcome to a copy.
If you remove parts, check the back for a part #. That may help in buying new ones. Also, if you remove a bottom, keep the old parts, as they are valuable.
Hope this helps. As you progress, keep us posted on the progress, and I can help you find sources for what you decide to replace. I have had fun disassembling mine, sandblasting and painting it, and putting it back together with new parts.
Lastly, if your plow is the model I think it is, it has no protection to protect it from striking an obstruction (i.e. large rock) Most later plows had sheer pins or spring mechanisms to protect them. So be careful when you plow. I was pulling mine with a 70 h.p. tractor in rocky soil, and damaged it twice. The last time did major frame bending and broke four 3/4" grade eight bolts. My new plow restoration is a model with trip protection. My feeling is that this plow was designed for smaller tractors and better soil than we have here.
Good luck!
FWIW....a Dearborn 2 bottom in good shape will sell for $400 or more in most areas. 
