273 hydraulic cam/pushrod/adjustable rocker combination.

I'd measure the installed spring height at this point. Stock is 1.685" from head to bottom of retainer. See what that dimension is to start to see if the valves are set up right, and to see if the rockers may be at an 'off' angle.

As for knowing the head and block milling, if it is not known, then it would have to be partially dissassembled. No the first time weird things are found in an engine...unfortunately.