Neal barker

I've just got pulled into a job where the customer told me the job was fitting a door and frame, I asked if it was standard timber door and frame and they said yes. I turn up and find out he has a fd30 for a fire exit door and frame to fit door both are 9inch to heigh, Am I right that it's still not possible to modify the door or frame in any way beyond manufacturing instructions. I have for now re measure brick to brick so he can try to get a set to fit properly. It's in a salon for the rear exit out onto carpark and the old frame and door are so rotten that it needs replacement asap I am clued up for internal work on flats and domestic but commercial like this I would rather try to find out