FIXED HANDLING PROBLEM-Question on Tires and handling? "Circuit Rider"

[70cst]

I have done a lot of searching w/o finding answer an answer. The Circuit Rider has Goodyear 285/60r16 tires on all four corner. After driving about 200 miles the last few days the truck just doesnt seem to handle right. These tires were on the Torq Thrust II's when I bought them back in 2008 (they were used then) so the questions is...what might be the possible cause of this? It has a 2/4" drop with new shocks and fully rebuilt front end.
Would new tires improve this situation? All I know is when I get up to 55-60mph I am not comfortable with the handling of my truck. It almost feel like it wants to wonder left to right....not a lot but a little but enough that I do not feel comfortable at highway speeds. Ideas and thoughts???

When I take the truck in for a final tune up next month I want to have some ideas as to what to look for. Thanks in advance.