I agree.
From what I could find, the taller flat top, no valve pocket 318 pistons are basically 1.74ch...... which would require the block be cut .060 for zero deck height.
And, that could easily be enough to warrant a shorter pushrod, especially if the heads have been milled, valve job, etc.
On the other side, the cam has more lift, so the base circle should theoretically be lower...... which helps with the pushrod situation.
Lots of unknowns here.