I have had later model liner on my 71 in since the early 90's. They work great and undoubtedly the best thing you can do to protect the cab mounts in a place that salts the roads, it will prevent rust.
The second place is the back of the cab, they also had plastic panels that protected the back of the cab corners. I did NOT put those in the first time, and I am paying on this restoration. The cab mounts lasted beautifully, the cab corners and inside panels disappeared.
71 F-100 SB 4x4, 445 FE, RPM intake, 750 Holley, 4 speed, 4 inch softride lift, all poly bushings, Duraspark, integral PS, most mods installed since the 80's (except the 445!)
70 Mustang Sportsroof 489 FE, EFI, TKO-600 5 speed, 4.11s
07 HD Streetglide, 96 cid, 6 speed
08 F-250 6.4 Crew Cab SB 4x4