I agree, but I've found it hard to measure up travel with leafs.
When a shock is operated too close to bump or jounce it doesn't last long.
I would take the stackup value (lift value of springs, shackles, blocks<shudder>), and use that as a basis to tentatively select a set of shocks. Then, without shocks, I would hang the vehicle by the frame in front of the rear wheels to get the droop. Measure from the axle side shock mount to the rear K frame. That's the shortest the shock needs to be to get the most down travel, and compare that to the extended value of the chosen shocks. If that length or a tad longer -OK, if not, select a longer shock.
Then I would bump stop the up travel. The compressed value of the shock (-) the distance from the rear K frame to the bump stop mount should be about the size of bump stop.