Answer to "Upgrade the Logic Board (Core i5)to Core i5 w.9Ghz?[Edited]"I’ll chime in. I upgrade my 2012 to a Late 2013 this way. Both models are built EXACTLY the same and have the same screw mounts. I would suggest buying a new board WITH the CPU on it. Then you can add a 3770s i7, and one of Apple’s blade SSD and then make a fusion based iMac. (Literally what I did) The 2013 boards are different by the fact of the socketed processor and the added GPU. Bump it to 16GB as well. A solid iMac then.
Answer to "Upgrade the GT120m GPU to 5750m from 27" iMac"Not sure if it would actually work. I’m in your same situation except mine works for a bit, then freezes up. I tried using a Radeon HD 4670 from a 2010 iMac, and my iMac didn’t show an image. Then again, I didn't let it boot all the way to see if it would actually show something. (Didn’t have enough time to properly test.) I need to get another GPU on my hands and see if the Mac will recognize it once in the fully booted stage. I also want to try and see if I can run it without the GPU and just use the integrated 9400M for the time being. That would get me along until I can get a Radeon HD 4870 to install.
Answer to "Swapping displays between early 2011 and mid 2012 mbp 13 inches"I have tried this on the 13" and 15" MacBooks and their connections are not the same at all. They are totally different LVDS connectors on the boards. The 2012 display will fit into older models, but it's not true going the opposite direction. The 2009-2011 all use a similar connection, and the 2012 brings forth a new one. It sucks because they've been compatible up until the 2012. You can even use the HD webcam on a 2010 model since it uses the same connection as the 2012, it's just placed lower.