[Kurt in NJ]

In my opinion the valve seats have be cut too deep especially the #4 exhaust and looking at the block deck surface there is a lot of pitting from rust ,the block deck should be resurfaced after having valve seats replaced .
the heads of some of the valves look rust pitted too.
I would suspect some of the valves are not seating as good as they should due to rust pitting on the valves an seats.
getting the valve seats back to the proper height will improve performance— it did wonders for my car.
It may not what you wanted to hear and just lapping the valves may make some improvements but the heads of the valves should be above the deck surface.
I would take a coathanger and go poking around to break loose as much scale as possible and use a drill bit to clean the small “steam holes “ to their full size too.