Monroe air shocks

so this is from their website. looked up shocks for a 70 duster.

"Ideal For Hauling, Monroe® Max-Air® Shock Absorbers Can Be Inflated Or Deflated Up To 150 PSI To Maintain Level Height With Additional Weight Up To 1,200 Lbs. (Capacity Is Limited By Vehicle Suspension, Tires And Transmission. See Vehicle Owner's Manual.)

MAINTAIN RIDE HEIGHT UNDER LOAD -- Air Chamber Can Be Inflated Or Deflated Up To 150 PSI To Maintain Level Height With Additional Weight Up To 1,200 Lbs. (Capacity Is Limited By Suspension, Tires And Transmission; See Owner's Manual)
EASY TO ADJUST -- Special Air Fitting Resists Air Leakage And Ties Into Factory System (Where Applicable) Or Manually Inflates With An Air Compressor; Pair With Monroe Air Shock Accessory And Shock Air Hose AK Kits (Varies By Application)
EXCEPTIONAL HANDLING -- Full-Displaced Valving On Compression And Extension Cycles For A Smooth Ride
BUILT TO LAST -- Hardened And Precision Ground Piston Rod For Consistent Performance, Sintered Iron Piston For Enhanced Durability And Longer Service Life And Lubricated Air Sleeve Reduces Friction For Smooth Operation
CONSISTENT RIDE -- OE All-Weather Fluid Contains Special Modifiers To Handle Extreme Temperatures And Help Reduce Friction And Ensure Smooth Rod Reaction".