I know I'm limited in my choice of chainrings because of the brazed on Fd mount. Can anyone tell me just how limited the range is? Will a 50-tooth ring work? I'm pushing 60 and don't think I can push a 53 for any length of time.

Here's the frame (nice, isn't it; 130-mm rear spacing):

http://page2.auctions.yahoo.co.jp/jp/auction/b148354689