By giving the fin a bit of height (will look it up) remove the protruding things on the back of the engines, shortening the darned thing and finally using the flat tail cone.
https://www.google.com.au/search?q=airbus+a320+vs+737-800&oe=UTF-8&hl=en&client=safari&gws_rd=cr&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=hwEUUtiNK4XmiAfBhIDoCw&biw=1024&bih=672&sei=iwEUUuOcIMLFkgXU7oGQCw#biv=i%7C84%3Bd%7CEMbZLdhSLlc-7M%3A
this drawing is probably most helpful, cant seem to find the one i used