OSHA requires in 1910.178(a)(4) that employers get the manufacturer’s prior written approval for modifications and additions that affect capacity and safe operation of a forklift. Further, 1910.178(a)(5) requires that if the truck is equipped with front-end attachments other than factory installed attachments, the user must request that the truck be marked to identify the attachments and show the approximate weight of the truck and attachment combination at maximum elevation with load laterally centered.