Can I marble two cakes that call for different cooking temperatures?
I have found that as long as the two recipes don't have a huge variation in baking temperature (and as far as I have found, 25 degrees is not that huge of a variation), as long as they bake for a similar amount of time, it turns out okay. What I usually do is set the oven at the lower temperature for the indicated bake time (in your case, 2o minutes), and then check them at that time to see if they are baked. Usually they are, or they are really close and only need 2-5 minutes more to be done perfectly.