Rudder gyros definately can be beneficial in some airplanes and not so important in others. I use three of these:
http://www2.towerhobbies.com/cgi-bin...?&I=LXL313&P=7 in a four engine Kaydet Senior and in two Wing P-38's These have received benefits from its use in several ways: With the quad the chief benefit is better throttle up t/o's due to the additional directional stability as the four engines tend to come up unevenly in many cases. Of course the big advantage with the 38's is the few extra seconds it buys you to "identify and react' with the appropriate rudder response which is always rudder into the good engine, not aileron. There are other actions such as power reductions depending on your configuration and position but the big airplane survival tool is 'Rudder not aileron into the good engine'.
Good examples of airplanes that it would be a good idea are any fairly heavy wing loaded airplanes such as that nice 310/320 you got there. I,ve done a number of twins that are fairly benign and fly just fine all day on one with just a little rudder imput such as a Seniorita with a pair of 30 FS's I put together for helping folks with learning the technique.
If this is your first multi then please consider doing a more benign type first such as a Twin Star or a Twin Air. Its always good advice to get with someone who truly understands the technique to serve as a mentor rather than someone who has just survived twins because they never had an engine out and idea of survival is to cut power and land wherever you may be.
If you use a gyro then the simplest form is all that is needed, expensive rotor gyros with adjustable gain from the ground and ability to switch on/off from the ground is total overkill for our application. There is never a need to turn it off it will not fight your manual rudder use. The unit linked above has worked well for me and the rudder is mearly plugged into it and the pigtail is plugged to the Rx. and it is mounted with its axis vertical somewhere near the CG thats it. There are to adjustments: a centering adjustment and the gain. Usually start at fifty percent and thats all that is needed.
John