Most aftermarket exhaust systems like Summit, Magnaflow and TTI, put the mufflers in front of the rear end where the factory put the resonators. They don't put anything at the back where the factory mufflers were.
Generally, the closer the muffler is to the manifolds/headers, the more raspy the exhaust sounds. With mufflers at the back, the exhaust might be a little quieter and won't be so raspy. The problem is that the mufflers you have now, probably won't fit next to the tank very well. They are oval instead of round. Why are you thinking about moving the mufflers? Are the 40s too loud or do they drone? You can add a small straight through design muffler at the back to tone down the noise. Lots of people end up doing that.