If you want to dabble in it, start with 1/4", Technics are all great, 1500, 1506 and the 1700 are great decks, the difference is 2 vs. 4 track and auto reverse, a Tandberg in good condition you cannot go wrong with, Otari makes a good deck, but I would not start with that deck unless you know that you r2r is want you want to get into. They do make plenty of 1" decks, but they are not 2 track, they are all multi track and unless you plan on doing mixing, etc, are way beyond what you need. As previously suggested, I would look on the vingage r2r site from Texas, he is very knowledgable and helpful. You can ask him questions directly, he monitors the r2r forum on audiokarmha forums.
Travis