As noted in the product descriptions for Lift Master forklift fork mounted booms the standard dimensions for the fork pockets are 20" or 24" depending upon style. Additionally, pre-engineered fork pocket spacings and fork pocket sizes are available. Typically, center to center dimensions of 24", 30", and 36" are available on most models/capacities, while some offer 11" as a standard configuration.
Call or write for your availability and cost for your application.