... upper pushrod bearings ....
Connecting rod. That's what confused us. The pushrods are the ones between the tappets (or lifters) and the rocker arms.
Rocker arm bearing wear is usually the first to cause low oil pressure. Since TH's oil pressure is good, I wouldn't expect wear there, although removing the oil filler cap with the engine running will allow visual inspection for excessive oil flow.
Rod bearing wear will show up as noise.
Main bearing wear will also cause low oil pressure.
Thrust bearings could be an issue. End play in the crank should be between 0.0025" and 0.0055".
Also if the rubber foot on the timing chain tensioner or vibration dampener is worn.