Is there even confirmation that there are heating elements in the steering wheel?
The Canadian market GT has an optional heated steering wheel. So the functionality exists, but to get to work for a US GT, you would need to:
1. Obtain the Canada market part number for the heated steering wheel and source it.
2. Obtain the Canada market part number for the switch that controls the heated wheel function and source it.
3. Determine if the existing wiring harness in the US market GT includes the plugs for the heated wheel and control switch. If the harness is already set up for it, you would install the new wheel and switch, and be good to go. If the harness does not include plugs for the wheel and switch, than you would need to tie in to another power source for the wheel's heating element and custom wire the switch to make it work.
bottom line is that it is generally doable, but at this point, I have not been able to get a hold of the Canadian part numbers for the heated wheel and switch, so cannot try buying them. If I had the part numbers and could source them for relatively low cost, I would give it a shot. Even if the existing harness doesn't accommodate these on the US cars, the wiring to make it work would be pretty simple to rig up.