Could A Vibration Be Worn Front Struts And Rear Shocks?

My wife's 2007 Chevy Malibu SS has a pretty significant vibration like a very out of balance tire(s) that starts at about 55 mph and mostly goes away at 62 mph or so. Then comes and goes over 65 mph. The car has 79,000 miles and Goodyear Eagle LS tires (same as the car came with when new) with about 5,000-8,000 miles on them. When the replacement tires were new there was a more serious vibration over 50 mph that turned out to be a bad tire that Goodyear replaced. The tires were originally balanced on a Hunter Road Force balancer and the car drove pretty smooth. During last winter, I took the summer tires and wheels off and put the mounted snow tires on. Other than the normal noise and roughness you get from fairly aggressive winter tires, the car drove well with no vibration. Once I had the winter tires and wheels taken off and the summer tires and factory wheels put back on in the spring the vibration mentioned above started. I had the guy who services my vehicles rebalance all the tires a couple of times as well as to swap them front to rear but the vibration didn't go away or change. Everything in the suspension has been checked as well and is tight. The vibration seems to change somewhat depending on the road. Less pronounced on a smooth road. So my question is whether its possible or likely that the original worn out front struts and rear shocks could be what's causing the vibration because they are not keeping the tires planted to the road?