There is nothing wrong with those readings. The rule of thumb is that the highest and lowest readings should be within 25% of each other. The math is like this: 165 (highest cylinder) X .75 = 124. You lowest cylinder is well above that (140).
Without more to go on, there is no indication that you need to pull the heads to replace the gaskets.
Also, head gasket failure on this engine is extremely rare.
What are the symptoms you're chasing?
