The good news (sort of) is it a Workhorse chassis, not a R4R with the trailing arm recall. The clue is "new tires" which means they probably put too much air in all your tires now. You need to weigh your axles and adjust your tire pressures for the load, not max sidewall pressure. Before spending money, check your tire pressures as they are probably inflated to max which will cause tail wag. Besides your seat there is a sticker which will give you a better recommendation of what pressures to run in not able to weigh this week.
With two people and a tape measure you can check the toe in on the front by measuring between the same spots on the side of the tire (front and back). You want a max of 1/4" less (toe in) on the front measurement.
You can also search on here about "track bars" and Koni shocks.
This post is my opinion (free advice). It is not intended to influence anyone's judgment nor do I advocate anyone do what I propose.
Sold 04 Dynasty to our son after 14 great years.
Upgraded with a 08 HR Navigator 45’...