I installed a BlueRail receiver (with sound) in a Williams E7 and a Weaver RS3. Initially the sound comes out of my Ipad, but in the E7 I installed a bluetooth speaker/board I got form Target for $5. I installed a 1" cube bluetooth speaker board in the RS3.
The E7 had plenty of room, the RS3 was tight but I managed to get everything, including the 9.6v NiMh battery (1"x1"x4"), inside the shell.
Here's some youtube videos I made a while back, not great quality but it'll show you a few things: