The easiest way to convert it is to resize. You just have to make sure you uncheck the Lock Aspect Ratio (and make sure you check next time you use it).
While this produces a usable template, it is rather distorted.
The better way is to crop it to the correct size you need. I open a new file at the size I want it to be and flood fill with a bright color.
The next thing is to reduce the size of the template's size so that it matches the largest size of your new file, in this case 11" vertical
Now drag the flood fill from your new file over to the resized template. Reduce opacity and place over the predominate part of the template.
While you still have the flood layer selected go to Selections>Select All; Selections>Float; Selections>Defloat (or contr a; contr f; contr shift f on keyboard).
Then go to Image>Crop to Selection (shift r on keyboard). Delete the flood filled layer.
You now have a template in the size you want without the distortion caused by resizing with the lock off.