Basically edit profile
Allow Beta versions and select beta 1.7.3
Override the minecraft save directory to C: (...) .minecraft/MC_beta
save profile and download and play game.
Then you will see all your normal saves (MC 1.8.3 etc.) instead of an empty list for only beta saves.
also options will be overriden and any other file/folder is just used in the regular .minecraft folder.
the MC_beta folder remains COMPLETELY EMPTY!
It works like a charm with MC_alpha though (alpha versions of minecraft)