Mullin, first things first. You now have the timing chain exposed. Do yourself a favor. Stick your finger over the #1 cylinder's spark plug hole (all plugs removed) and have a friend turn the engine clockwise. When you feel pressure on your finger tip and air pushes out, turn the crank until the dot on the crank's timing gear is pointed straight up. The keyway will end up in the 2:00 position or so. You are now at TDC on the compression stroke. The dot on the cam's timing gear SHOULD be exactly straight up. I use a steel ruler to verify both dots are lined up and exactly centered over each gear. My feeling is, the cam gear's dot will be tothe left of center. Meaning the cam timing is retarded. The pressure reading you got has NOTHING TO DO WITH STATIC COMPRESSION RATIO. It has to do with dynamic compression ratio that again, cannot be figured by using strictly the pressure reading. You dont need to think about shaving heads or retainer to guide clearance. You need to do some checking. Post a pic of the ruler and dots either lining up or not. Witht he timing cover off, you can ignore where the rotor points, if you can see the piston top, etc. use the dots. Crank dot points straight up, cam dot should also be slightly ahead or in line with crank dot. It's that easy.
Now, as far as cam size goes...They changed the mechanical cam for hydraulic, so they probably just replaced the rockers for non adjustables for ease of maintenance. It's fairly common. You cannot replace a cam in some 360s with anything over .450, because some 360s have exh valve rotators and they are almost twice as "tall" as a std retainer. So they will hit the guide at full lift. You can replace the rotators withstd retainers, and run the same deals as a std mopar LA. In that case, I use .490 or so lift as max. I have run .484 cams with no retainer to guide issues on stock guide 340s. I also now make it a point to have the guides cut down for modern seals on every head I do to avoid that issue. Thier shop may not have been a performance type shop tho.
Good luck.... You're on the right track, just stay focussed. Worry about what you have, not what you need. Worry about what you need when you make sure what you have isnt put together wrong. It sounds to me like it is.
