[peppermrj]

Sounds like you checked all the easy stuff.The vacuum gauge readings would indicate a burnt valve or bad valve clearance according to the book. I would start with #1 since that is where your compression is low. Bring it toTDC and blow air into the cylinder thru the plug hole. Then listen at the carb for the hiss. My "guess" is you might have had a vacuum leak on #1 and fryed the intake valve. Hydralic lifters aren't really adjustable except for adjusting the rocker. I don't know that they could cause the valve to hang open.

The only other things would be a bad head gasket,cracked head,or bad timing chain/gears. All of which have other symptoms that go along with them.
Good luck and let us know how you make out.