As mentioned, you’re probably out of luck. The width of the tail end is wider where it fits at the tailgate opening than the bed is wide. I haven’t been on FWC’s website in quite a while, at one time they had a “Fit Chart” for the older campers. That said, it may pay to double check your bed measurements, shape and any FWC you’re considering. For example my camping buddy of days past got lucky and his old Keystone fit his new Chevrolet 2500. He did have to set it on 1 or 2 inch stringers so it would clear the curve at the rear end of the bed floor.
The other opinion is to modify the floor pack/back of an older FWC to fit. A search of the threads on here should yield a few examples of those who did just that.
Good luck with your search.