Steering inputs and responce are excellent are relative speeds, however once speed reaches 75 to 80 mph steering feels loose as though there was a small amount of play in the wheel.

Is this normal? Could it be attributed to tires or suspension setup?

Wondering while I wander.

 

Could be alignment problem......

 

I'd bet on something loose or worn.
Alignment might cause a bit of wandering but at the high end of the 80mph range mine actually settles (aerodynamics?)and the steering feels noticeably tighter if that's possible.
So alignment wander...yeah possible, but 'loose' has gotta be something else.
For grins, try another road for speed/handling testing, you never know. while you are at it get a good tire pressure gauge.
Last but not least, Nicole started a post on a strange shimmy a while back and there were a number of responses.
I think this was AFTER her loose half shaft problem though it might have been related.
Which brings us to another interesting area: if you have an oddball wobble in the rear it can feel like something is amiss with the front end.
So check your shock mounts, hardware, & bushings.
Possible wheel, or, tire out of round, wheel bearings, half shaft hardware loose or missing, tire mounted in wrong direction. Improper ride height, not corner balanced for weight.
Then there's the front end...Oh my God!
Do the simple stuff first,and as always check the archives, and the Greg Nichol's site.
Good luck and keep us posted.
BTW
EVERYONE focuses and tend to fine tune the senses when we start seriously violating posted speeds.
Might have something to do with self preservation.

 

John: Thanks for the info! Checking the tires tomorrow first thing as she has been sitting most of the winter.

Speeding? Naw . . . just trying to keep up with traffic around these parts.