OK, I removed the old spindle and it is indeed a 3T. Sheldon says that would put the overall length at 123mm and a symmetrical equivalent of 130mm. However on my ruler the spindle looks closer to 125mm. Original rear spacing was 126mm; I'm moving it to 120mm. So I'm thinking I'll try a 125mm (maybe 127mm) and see how it goes (I think I'd like to move the chainline in a hair.) If anyone has any other educated thoughts/guesses I'd like to hear 'em. Thanks.