Are MacBook parts interchangable?

Let's see if this helps....

There are obviously 2 aspects to compatibility: physical compatibility and working compatibility. I can comment on physical compatibility, but I don't have all the answers for whether parts are compatible once in the machine.

1. : Model A1181 MacBooks. The revisions of MacBook saw the following major changes:
   • The original machine is most commonly called Core Duo. The battery is 10.8 volts and 55 watt hours. This is the same for all revisions of A1181 MacBook.
   • From the Core Duo to the second generation, known as Core 2 Duo, the heat sink of some Core Duo models and all Core 2 Duo models changed connectors. Core Duo machines have 2 Airport antenna connectors coming from the display assembly, and Core 2 Duo machines have 3 antenna connectors.
   • Within Core 2 Duo, there are 2 revisions: Late 2006 and Mid 2007. The compatibility difference relies in how the battery connector attaches to the logic board. Models with "Energy Star" printed on the board in the RAM slot have 2 fewer pins on the battery connector, and the logic board has 2 fewer holes. Models without "Energy Star" printed on the board have 2 more pins than non ES models.
   • For the next revision, called Santa Rosa or Late 2007, Apple changed most of the connectors in the machine. The fan, inverter cable, speakers, Bluetooth, and PRAM battery have JST connectors and are therefore incompatible with previous machines. The heat sink went from 2 to 1 thermal sensor connectors also, making it incompatible with earlier machines. Finally, the PRAM battery was moved from under the board to near the right speaker, making the lower case of previous machines incompatible. All battery connectors are Energy Star version for this version.
   • The next version, known as Penryn or Early 2008, has the one difference of returning to 2 Airport antennas coming from the display assembly. It is otherwise compatible with the Santa Rosa machines, but not earlier versions for the same reasons as the SR machines.
   • The next version, known as Early 2009, changed the optical drive connection to a SATA-type connector. Therefore, the optical drive and cable are not compatible with earlier machines. Also, the heat sink changed again, and different screw holes means that the heat sink, logic board, and lower case are not compatible with previous machines. It also eliminated the PRAM battery and updated the Bluetooth to 2.1.
   • The final version of A1181 MacBook, known as Mid 2009, only had one change. The heat sink eliminated thermal sensors entirely. This does not affect the logic board, however (the port is still there, but isn't used). Therefore, the Mid 2009 version is fully compatible with the Early 2009 versions, but not earlier versions.
2. Next MacBook Airs:
   • The original MacBook Air is marked A1237. It features a Micro DVI port and a 37 watt battery.
   • The second revision MacBook Air is marked A1304. It features a MiniDisplay Port port, which makes the port hatch assembly and upper case incompatible with the original version. Also, the multiPod Touch ribbon connector on the upper case has shifted to the right, making the trackpad control cable and upper case further incompatible. The audio board connects the same way, but is internally incompatible. The heat sink and fan are slightly different and incompatible. The hard drive and hard drive cable connect to each other differently than the original, making it incompatible. Finally, the Airport/Bluetooth cable and processor clamp are shaped slightly differently and are incompatible.
   • The most recent revision MacBook Air is also marked A1304. The battery was updated to 40 watts. It is otherwise compatible with the 2nd generation, but incompatible with the 1st generation for the same reasons as the 2nd generation.
3. The Model A1342 MacBook (otherwise known as Late 2009 Unibody) has a 10.8 watt battery. The machine uses JST connectors throughout, has a SATA type optical connector, and the case components are incompatible with other MacBooks. The display connector is also different than any other MacBook.

Having all THAT said, all three machines (A1181 MacBook, MacBook Air, A1342 MacBook) have different battery connections and different logic board form factors. The A1181 MacBook has the biggest logic board. The MacBook Air has a logic board about half the longitudal length of the A1181 MacBook. The A1342 MacBook has a logic board somewhere in the middle.

Well that's all the information I can think of that I know that is relevant to your question. I hope some of it is helpful!