Swapping Engines... (? about compression)

I have a 1989 accord, carburated. I've had some problems with it recently, actually completely dead now after getting a blown head gasket replaced. I'm looking at putting a whole new engine in. I've located a couple at a junkyard (we take it out and no warranty) that I can get for $150, a great deal considering everyone else is asking for $4-500 (but already out, tested and running). Now the one we've looked at for $150 seems to be in good shape. Car has 120,000 miles on it and was wrecked horribly so I assume it was running well at the time it arrived at the junkyard. Now here is my main issue. We ran a compression test and got 150, 110, 110, and 150. That is where I get lost. For the middle two cylinders, they have enough compression that the headgasket isn't blown, but they still are significantly lower than they should be considering the compression on the outer two. What could be causing this? One person has told us that when the engine stopped, two of the the cylinders would be open and two closed and that would possibly allow for two to be rusted or something like that that could be self fixing after running a little while. Also, a second car in the same junkyard which had also been wrecked gave similar compression readings; high on outside two and significantly lower for the middle two. Is this normal for a car that has been sitting for a couple of years? Is it a big problem?... Sorry for the long post (I'm not really sure what I'm asking), but if anyone can pull some useful info from what I have said and get back to me with anything, I would be very appreciative. Also, I will check back regularly so please ask any questions you might have to help out. Thanks a lot.
David