1 baking pan, dough for 2 loaves. What do?
Is there a very special reason you want to bake it in a bread pan? 

The recipe is solid enough to be baked free-standing, in any bread shape you like - batard, boule, and all the fancy ones. It actually will be way too dry if you tried to incorporate the whole flour (but notice it does not direct you to do so). So you can shape, proof and bake completely without a pan, simply place it on a baking sheet or pizza stone, or onto the bottom of a cake pan. 

Alternatively, you can bake it in any other pan you have. For example, round pans such as cast iron paella pans make great round-low breads, although I must say these are better for a large family dining together, since they are not that convenient to cut into slices. But lasagna pans, casserole pans, cake pans, etc. will all work. Or try for once a dutch oven bread and see if you like it. 

So, unless the exact cross section is very important to you, just follow the recipe properly by keeping the given times and baking together, no matter what pan you are using (or not using).