It is absolutely possible, Ilmars. You can have both 32-bit and 64-bit versions pointing to the same .dat and they will both work (that's all I do here). I would still back up your .dat though - anytime I do something a little out of the ordinary, I make sure that the .dat is copied off to a safe place. Thankfully, only in the most extreme cases have I ever had to replace my .dat (this would be something that was my own fault lol).
Also, you can check out the -datadir (or whatever) command line parameter in the help document (hit F1 when VA is in focus to see the help doc). It allows you to specify an alternate location for an instance of VA to use.
Hope that helps!