From our freinds at Morse Mfg for finding this answer to the question of getting hassled by the manufacturer of updating the forklift data tag:
An OSHA inspector stated that if an employer (truck owner) can't get the lift truck manufacturer to cooperate, there is an alternative. He said there is an OSHA letter of interpretation that says "...if the employer has ... written approval from a qualified Registered Professional Engineer..." He said the employer should keep such a written approval in their files.
For the complete info, see letter of interpretation 1910.178(a)(4). The relevant wording in that letter is:
"...written approval from the manufacturer of a powered industrial truck is required for modifications and/or additions if the modifications and/or additions affect the capacity and safe operation of the truck. However, please be aware that OSHA would consider the lack of manufacturer's approval to be a de minimis violation if the employer has obtained written approval from a qualified Registered Professional Engineer after receiving no response or a negative response from the powered industrial truck manufacturer. If the manufacturer's response was negative, then the engineer, prior to granting approval for the modification or addition, would need to perform a safety analysis and address all safety and/or structural issues contained in the manufacturer's disapproval...."