This is what I used, it seals up the gap between the tailgate and bed. Just make sure and clean the surface with rubbing alcohol before applying the seals.
I’ve had no fitment issues or leaks. I’ve washed it several times and no water got inside the bed. I did seal around the tailgate with weather stripping which keeps the inside of the bed dust and water free.
I ordered mine with the otr coating, basically it’s been coated with bedliner. It’s not an exact color match with the hardtop, but it’s close enough for me. I almost went body color, but I go off road so I knew I would scratch it up. With the otr coating ($450 option)I don’t have to worry...
A bunch of stuff in the last 2 weeks: Red Rock bed sliders, Rough Country molle panels, mounted two 3 gallon Rotopaks, Power Tank 5lb propane tank mount and A.R.E Classic topper.