As a general rule, stick with conservative (low baffle, medium to large chamber) mouthpiece designs while you develop as a player.  You do not want to be in a position of being dependent on certain mouthpiece features as a substitute for good technique.

The chabmer size rant is not a load of junk.  The ideal is to have a mouthpiece that can be adjusted so that its interior volume equals the "missing" volume of the cone that would theoretically extend beyond the end of your neck to its vertex.  That is much harder to achieve with a smaller chamber and intonation problems can result.   Some horns are much more forgiving than others with regard to the range of mouthpieces that can be accomodated.  The only way to tell for sure is by play testing.  But your horn was produced in the era when low baffle, large chamber pieces were the only ones in existence.  

Kangaroo pads are nice (I use them) but the hardness of the felt used with them makes them unforgiving to install.  Unless you're sure the toneholes are absolutely level, and the keycups are perfectly aligned, forget it.  Better to stick with a softer backing unless you're going for a full overhaul so there is no mechanical play and everything is in perfect alignment.  

There are a number of silver cleaning, polishing, and restoration products that you can use without damaging the finish.