More number crunching……
The intake valve pocket depth on an Icon piston for a 408 is .243” deep.
The tappet lift
@tdc of the intake lobe on the XE295HL, when installed at 106* C/L is .120”.
Multiplied by a RR of 1.5 puts the valve lift at .180”(and that’s not taking into account the lost motion from the way less than ideal lifter-to-pushrod angle on the SBM).
That puts the intake clearance at.060”+.
Then
add in whatever the valve drop on the heads is, plus the gasket thickness.
Something has to be pretty far from the norm to have the intake valves touching the pistons(zero clearance).