Buy a set of 16 of the soft checking springs and simply swap the real springs out for the checking springs while they're off getting tested. Be aware you need to shop around a bit cuz some of the parts vendors ask as much for 2 springs as others might for a set of 8.

Or, if Dwayne suggested only needing to send four, pick 2 intakes & 2 exhausts (which I suspect was your plan) to be able to see if there's a pattern in load degradation between the two sides.

So, what pressures & heights are (were?) the springs set up for?