[Mike C]

The measurement you want is from the center of the hub to straight up to the bottom of the fender.

Wheel and tire size can affect the ground clearance as well as the height of the roof from the ground but don't have anything to do with how much you lowered the suspension.

On my 69 short step the 2 1/2" drop spindles and 2" ECE small block springs lowered it almost exactly 4 1/2".

And FWIW, the DJM flip on my 5 leaf HD spring C10 dropped my truck 7". On a leaf truck not just the arch of the spring but the thickness of the leaf pack contributes to how much it's lowered based on how high it was to begin with.