If the capacity of the truck is not shown on the capacity plate, then it's not safe to perform the lift. Correct action in this case is to contact the manufacturer and ask them if the lift is safe and for them to send you an updated capacity plate. Shame on your employer for buying a truck and not "specing" it to the loads expected to be lifted. The "inch-pound" rule is a rough way to determine whether a load with a +24" load center can be lifted but it only applies to lifting the load off the floor - not up to 200". Example: measure distance from fulcrum (axle of front wheel) to load center in inches. Multiply this by the safe rated capacity to yield "inch-pounds." Divide the "inch-pounds" by the extended distance (fulcrum to +24" load center) and this yields the reduced weight - new safe capacity. But don't use this for lifts above 4". Best bet: consult the manufacturer.