Cam does not make a lot of sense either. For a CAM to effect a compression test the intake valve needs to have almost no movement. Even if the cam was only opening the valve .05" you would pass a compression test but it would cause a bad shake at idle. At 200 RPMs (cranking speed) the valve does not have to open much to let air in because everything is moving in slow motion. A cam that would effect on a compression test would just be a miss at 1500+ RPMs.

You did say this was a running car? What the compression this bad before the head gaskets. Do you have access to a vacuum gage? or and air compressor? Vacuum gage would verify low compression. Low compression with normal vacuum would mean the cylinder was leaking down during compression stroke. Low compression and low vacuum would mean the intake valve was not opening enough to draw in air Or it is suck air from the exhaust valve. If you had Low compression and normal vacuum you could then plug in your compressor into your spark plug hole and listen for where the leak is.

3800 is a pretty solid motor. To get 4 cylinders that bad would take an event like a major over heat, serious over reving (normally end is a spun bearing) or it would take time, meaning you have been driving a car with bad vibrations and missing over a extended time period.