Dual major in mathematics and physics
I think that nearly every university would require your grade as represented in your transcript - your overall grade. If you hide that, then you could be accused of misconduct.
However, you can, in other materials, point out that your physics grades are higher and report it. There is no problem with that. Perhaps a simple phrase in a sentence in the SoP would serve.
Being &quot;selective&quot; permits all sorts of potential abuse.