I shut off the main water supply as I am attempting to replace my toilet tank. When I
Looked underneath the toilet, both wing nuts are rusted, and broken off. I sprayed WD
To try to loosen without any luck. Any ideas please

When I
Looked underneath the toilet, both wing nuts are rusted, and broken off.
Don'tcha just hate it when that happens? When that happens to me I take a hacksaw blade and wrap some tape or a rag around one end and slip the blade under the tank and saw the two brass tank bolts off. Good luck, Tom

Working around porcelain forbids some of the best techniques, heat and impact. You will just have to go at it with Vice-Grips or Channellocks. Filling or grinding flats on what is left will help. I don't know how I got along without a Dremmel for so long.

A Dremel and a hacksaw both sound like fine options. However, if you are replacing the entire tank you don't need to be too gentle. You could break the tank if you can avoid breaking the toilet at the same time. Vice Grips are also good and you aren't necessarily turning the nut with the grips, just holding it in place. The screw driver slot inside the tank can be you point to apply force.