It always starts with a survey. The differences matter in proper fitting on your orderpicker. There are no standards. I have yet to come across an orderpicker with something other than 4" wide forks, conversely, Hyster/Yale's forks are 1.75" thick, Crown 2.0" thick, and Raymond/Toyota is 1.5". Standard lengths also are listed with differences in manufacturer's spec sheets that are available online.
Pallet clamp widths are not shown on spec sheets and within brands, there are new options.
The outside to outside fork ranges are also different, in fact, one brand list a different range for 24-volt trucks vs 36-volt trucks, I can't explain it. In fleets that have been in service for some time, there is also the possibility that someone on the 3rd shift ran into something and changed the width dimensions.
It starts with a survey click here