Deck height variance and pushrod length have very little to do with valvetrain geometry on an LA Mopar small block using factory rocker arms. The geometry is fixed since the shaft mounting and the size of the rocker arm do not change. The only thing a longer or shorter pushrod will do is set the plunger preload in a hydraulic lifter.
If the rocker arms are changed to any roller tipped rocker arm the geometry will be off and pushrod length will not fix it.
I do not know the actual deck height and the number is considered nominal anyway since factory tolerances allowed a fair amount of variance in the advertised number. This can be measured precisely by the machinist decking the block or roughly with a larger caliper while engine is apart. No real help since yours appears to be assembled already.