If in the US.
This a serious alteration/modification to fork truck and is frowned on by OSHA and sometimes state authorities.
If such a modification or alteration is done it has to have a factory stamp of approval and then could only be done by an authorized service station that was equipped to do the required test under load, no small task.
I would not attempt this on any fork truck. High mast trucks are high mast trucks alone.
I would give you the name and number of a person that did a similar modification except it would bring back too many painful memories of his stay in the hospital and walking with a limp.
I don’t have the standards or codes that apply to this , hopefully someone has the numbers of the standards.