It's good to read old timers discussing this sort of thing .
Some here may have dealt with older blocks having malleable cast iron that resulted in the deck pooching up around the threaded holes for the head studs .
? How to repair back forty + years ago when these (NOT Mercedes !) were new and so often had weepy head gaskets that held compression yet leaked oil & coolant ? .
Use a LARGE flat file across the holes, work like a charm .
Also many would hand paint a 1/2" wide stripe of flat white house paint around the perimeter of the deck or lay strands of copper wire.....
When finished this engine should have more dollar value than the chassis it's installed in
.
Keep going .