I just read through this thread, and I think there's an important point that has been missed. Compression and leakdown tests will not tell you if your valve guides are shot - they can't be used to determine this.
The leak down test is performed with the valves closed - no interaction with the guide. Likewise, the compression tester measures compression, which is done when the valve is closed.
Your oil consumption is high. 1 qt per 500 miles is what I call "area of concern." Worn valve guides will tend to overheat the valves, which can cause them to wear more, and possibly break off, destroying the entire engine. This, of course, is an extreme case - your guides would have to be seriously worn to have this happen.
Read this, lots of good info on the subject:
http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-1.htm
-Wayne