Got one of these from work today and tested it out. After 20 seconds, it was over 1000 degrees F". It was wired into the GP solinoid. Gonna try to rig it up on my 92 7.3 this weekend.
I have plans to do this also, but you may want to setup a different solenoid activated by the sharing the GP signal. The solenoid might not be rated for that extra current pull.
I really wouldn't do this if you still use the stock GP controller, if it sticks on that kind of heat can't be good for long periods. At a minimum the wiring insulation would melt from the resistance.