I'm out of AP Flour! But I have bread flour and whole wheat. I'm making sourdough sandwich bread. Should I wait until a grocery run? Or forge ahead?

Bread flour just has a higher gluten content. Works great for bread(hence the name)! You don't need the whole wheat flour unless you wanted to add whole wheat to begin with. The bread flour subbed with the AP flour 1 for 1 in the recipe should work out great.

Great! That was what I was thinking, that they'd balance each other out. Thanks for the suggested ratio! I'm going for it!

Forge ahead! Your bread will be fine. You might want to add a little extra water. But the increased gluten in the bread flour will balance out the effects of the whole wheat and come pretty close to AP flour. I'd suggest about 1 oz of whole wheat for every 8 oz of bread flour. Good luck!