Do not remember if this is the one but RAM had an increased gross weight approved by FAA and a STC issued simply by re mark of the ASI + a flight manual suplement.
Serviceable ( non-TAS ) airspeed indicators - remarked
[ If TAS indicator is currently installed, consult with your RAM representative. ]
<li class="Body-Copy">Gross Weight Increase STC and Flight Manual Supplement
T310 P [ + 270 lbs. Useful load ] [ GW from 5,400 up to 5,670 lbs. ]
T310 Q [ +170 lbs. Useful load ] [ GW from 5,500 up to 5,670 lbs. ]