Very nice build, your organization and attention to detail are really good. I believe Doug and Sluggo gave you good, knowledgable answers to the question about the seat tube curve. I would keep an eye on the welds for the down tubes at the seat tube, for crack formation and propagation. Also, at the seat stays welds attaching to the seat tube. Even paint cracking here will be a give away.
From my experience in fatigue and failure of steel tubing and welds (construction quality engineering inspections) unless you are subjecting the bicycle to some hard riding, and/or heavy loads, it should hold up quite well. These CroMoly Schwinn frames are truly well built and engineered, to the point of overkill and overweight. I'm building up a "kool lemon" Super Sport, 1972 year model now. Its nowhere near the nice condition, patina wise as yours is, but it should provide me a good, reliable around town and campus bike. Just as my '73 Continental did, back in the day, way-way back in the olden days.
The front derailleur, I'd give it a chance, I found an original for my build, getting the correct diameter band is the hard part. I punted on getting the original long cage rear derailleur, they are scarce and pricey. Reading posts from the learned elders here, I found a nice Suntour VSeven, long cage derailleur, on eBay for a decent price. Your cleaning and rebuilding are well executed, Kudos.
Well done so far, please keep us updated as you get things wrapped up, and put some miles on it.
Bill
__________________
Semper Fi, USMC, 1975-1977
I Can Do All Things Through Him, Who Gives Me Strength. Philippians 4:13
Last edited by qcpmsame; 07-07-21 at 02:28 PM.