Straight and narrow

Hey all, I have a 65 coupe with manual steering and I'm getting a lot of play in the steering wheel especially at high speeds and the car wants to drift from side to side requiring a lot of correction to continue straight. Is this a problem with the steering box? Something else? How would one diagnose a bad steering box? Any help appreciated. Thanks.

Did you check all the steering compoents to make sure nothing is loose. That is just something I would check out first but thats me.

Yeah, all the linkage looks O.k. and the Tie rod ends are new.

The tie rods was my next thing. How about maybe the tires balanced that will deffently make it try to go side to side. Also when my tires were not balanced it would have a little play.