Brad3104, My 1979 model? seems very similar to yours. The original components were Takagi Tourney crankset, Shimano Tourney brakes with 600ex levers, 600ex derailleurs front and rear, Araya 27"x1" rims on generic low-flange Shimano hubs, with the early uniglide freehub with 6 speed cassette. My seatpost, bottom bracket, stem and bars were SR and the size of the post was 26.8. Mine has a sticker at the top of the seat tube indicating double-butted CrMo, but no model designation. My guess would be Tange #2. Do you also have the freehub? Their is no bulge on the drive side, but the axle holds it all together. I'm still riding it to work every day! PGMikeT