Blank canvas, steel sided 40x60 pole barn. Thoughts on insulating, electrical, heating???

I agree with the radiant floor heat while you still have the chance. After the slab is poured with the heat pipes in it, you can heat it with a variety of choices, including 110/220 electric, propane, natural gas(if available), or even solar panels. The more you spend up front, the more inexpensive in the long run.