I'm not a big fan of gas tank coatings. I have a restoration shop for older cars and I've seen them fail a lot. Just last week I removed this:
.... from a Packard gas tank (and that's only part of it). The owner had it sealed about six years ago.
Just like paint, all coatings will fail in time. Once they do, they are a major headache to get out. I find that after most tanks are steamed, they still have a lot of their original plating inside. The orange rust color most people see when they look into a dirty tank is gas that has turned to goo. I think what a lot of people confuse is that rust itself is not corrosive, corrosives are corrosive. Rust is the result of corrosion. Even once a tank has a coat of heavy surface rust inside, it is pretty stable, just like pieces of sheetmetal people here own that are covered in old surface rust. Once they reach that point they stabilize and from there on out they rust very slowly. You don't see things rust away to nothing unless exposed to a frequent application of salt, or some such.
The other myth about coatings is that the inside of your tank will be forever clean, and that's simply not true. Most of the contamination problems people have from old tanks is the gas turning to goo, and the sealer won't prevent that. If you use your truck and keep fresh gas in it, you'll be fine, just like you are with your daily driver. My recommendation is to steam it out and use it as-is. I know I'll catch a lot of grief for having this opinion, but I've seen a lot of others catch grief for having used sealers in their tanks.