My steering wheel shakes considerably when braking at speeds higher than 60 MPH.
Braking at speeds less than that is fine. When it does begin to shake, it will quit at around 45 MPH. It may be by coincidence, but it started shortly after I had after market wheels installed(got rid of the steelies w/hubs). I had the brakes checked during my last tire rotation and they said pads and rotors were fine.
The size of the stock wheels are 15x6, 52.5mm offset. The wheels I had installed were
15x6.5, 45mm offset. I don't know if that is relevant.
Thanks for your input!

Over torqued lug nuts, or the wrong type. Today's cars, we call them wheel fasteners because it's getting pretty sophisticated.
By the way, some rims require a plastic spacer ring to match your hub diameter and must be installed.

It could also be that you lost a wheel weight and need to have the tires rebalanced.

My steering wheel would shake when I had new tires put on and they needed to be rebalanced. Did you have the wheels installed by someone else? Because you could just take your car back there and tell them the wheels need to be checked.

Thanks for your recommendations... hopefully I can get it resolved

Is the vibration more of a pulsing rather than a shake like a wheel out of balance? Sometimes a rotor is just out of tolerance and gets a bit grabby. I'd ask them to check the rotor again. Also, have your tires balanced again at a shop that specializes in brakes and balancing. I have had some jobs come out of the shop that were so sloppy they had 10 oz. of weights all over the place.