Electrical Issues?

[Kevinb1]

I'm new to this Forum and new to Volvos as well. I have worked on cars all my life, but mostly cars from the 50's and 60's. I would like everyone's opinion/help diagnosing a problem on a vehicle (2007 S40) I may purchase.
Here's the story so far....
6 Months ago a friend gave me his daughters 2006 Volvo S40 with a broken timing belt. He told me that he wasn't going to repair the car because of the cost to replace the head and timing belt. I took the car because I figured it wouldn't be that hard to replace a head, its turned out to be more than I had anticipated. I discovered that purchasing a used head was a lot cheaper than trying to have the current head rebuilt so I've been on the look out for local parts cars that I can pick up cheap.
Fast forward to last week
I found a 2007 S40 in really good condition that a guy doesn't have the time or money to repair. Here's the story on the 2007.
The current owner says the car will turn over but will not crank, so I went by and verified that it would indeed turn over. He informed me that he took it to a Mechanic after he bought it (not running) and had them work on it in their spare time. According to him (current owner) it needs a new wiring harness. I called that mechanic to ask more technical questions that the owner didn't know the answers to. The mechanic informed me that they are getting a lot of CAN codes when they put the computer on it, but could not recall the actual codes. He also told me that they can clear the codes with their OBDII and the engine will crank up and run for a short period of time, and then shut down. It will not crank again unless they clear the codes. He told me that they did not spend a lot of time on the vehicle because the owner did not want to invest a lot of money in it. So the auto shop told him that he could be looking at a lot of money to troubleshoot the problem and he'd spend a lot more than he wanted. The cars original engine had a broken timing belt and the owner before this gentleman had a used motor (80K miles) put in the car. When the motor was installed I have been told that it would run, but shut down shortly after they cranked it. That owner (that had the used motor installed) informed me that the car has gone into theft mode, so he sold it because the computer would have to be flashed and reprogrammed at a cost of $1200.
Since I have a complete parts car (2006) can the computers and the throttle body be removed and put into the 2007 to make it run?
I am thinking about purchasing the car because I have a parts car, but would like some ideas on what some of the issues could be based on the information given.
One Volvo specialist in my area recommended a hard reboot of the system to see if that would work.
What do any of you think? Is it worth investing $700?

[Kevinb1]

I guess it would help to say that I would like to get the 2007 running rather than replace the head on the 2006.