In theory, the stock uncut block is 10.725”.

With correct stock length rods(6.768”), and a crank that’s an actual 3.750” stroke, a piston with a ch of 2.067” would be down the hole .015”.
I haven’t seen any stock stroke shelf pistons any taller than that.
The Pro Tru piston is shown as having a 2.050” CH.

.030 over 440, uncut block, 88cc Head, cometic .027” gasket, Icon 9953’s......9.7:1.

The “correct” 68/69 440HP piston is a flat top without any valve pockets, with a 2.031” ch....... which would sit down the hole .051”.
This piston provides the same CR as the factory 6bbl piston.
The added CH of the 6bbl piston is to offset the loss of CR from the 4 valve pockets.