Tom,
If you can't fine the Insert that you need, the Line-X spray in stuff does rock.
Mine has taken the pounding for the last 4.5 years. Old engines and trans rolling around back there and oil and gas leaking on it. Moving field stone and gravel around for yard projects. The stuff is pretty tough.
It only about two hours to spray it and let it do the initial dry. It was fully cured and ready for use in 24 hours. It's cost more than an insert but it does have some resale value impact on the truck because it will last.
Rick