I have a 2001 3326King. It came with Goodyear Marathons on it.

As far as your question about using truck tires on the trailer, as long as they meet, (or better yet, EXCEED), the load rating,,,, I used to sell tires, and in my opinion, (and my opinion only),the answer is, yes, you can. (This is going to get a response from others)  

The "ST" on the tire means "special trailer". Those tires are made of a different rubber compound than car/truck tires. A car/truck tire will dry-rot just by sitting. Driving them keeps the rubber compound flexible, hence helping them last longer. Since a trailer usually just sits, (compared to a car/truck), the ST tires are made of a different compound than doesn't need to be "driven" as much to keep from rotting. So, if you watch the load rating, you can run truck tires on your trailer,,,, but,,,,.

Remember, this is nothing more than my opinion. I don't want to get a debate of any kind going here.

Mack