340 wall thickness & deck height

Jadaharabi said
The second part of my question is the deck height on the driver side I have a measurement of 9.606. At the rear on the driver side I have a measurement of 9.601.
On the passenger side front I have a measurement of 9.600 and then on the rear passenger side I have a measurement of 9.610.

Would this block need to be decked or squared up?

Yes, very much so..........though it is typical of what production machine tolerances were back in the day.........before square decking the block it would be good to know desired piston, rod, and crank, to know min/max cut required........cut once only