Just by name brand tires thats for sure,i dont care what any one says i never skimp on good quality tires,besides its the only thing that makes contact with the road unless your laying frame.lol
Also you have a vibration did you ever get the king pins checked also are you still using the stock drive shaft and if you are did you ever get the carrier bearing looked at my truck has a slight humming you might say when you get up there in speed which i would be safe to say is my carrier bearing,and i guess the humming i am talking about could be a vibration to.The trucks have simple suspension and drive train so it wont be hard for you to narrow it down.
Keep up the good work also truck is coming together just fine.