This past weekend I ran into a similar problem. I bought a parts car with a supposedly good 58 235 in it. We pull the spark plugs and did a compression test and found 3 of the 6 cylinders way low. I added oil and rechecked and still had way low compression. I pulled the valve cover and loosened the valve lash and rechecked. Much better, I found that I still didn't have much lash on a couple valves so I loosened them more yet. I did spray the valve stems with lots of penetrating oil just to make sure things were lubed good. In the end I got it to run, the more it ran the better it got. We bought it this past may so it sat all summer. I'm now sure that the motor is reasonably good so I can move forward taking it out. Keep at it and you'll get it to run.
