OK I got the frame from
RustyJames (thanks man!) and disassembled the frame patches. Incredibly, both places had tight-fitting
solid aluminum bars, not hollow or tubular. Lathe-turned to a diameter to fit 'just so' inside the tubes. Put in with screws and some kind of rubbery glue, like barge cement? Totally inappropriate type of glue — luckily, since I wouldn't have been able to get them out if they'd been put in with proper toughened epoxy.
The alu bars, the steel clamps, nuts and bolts all together weighed 516 g, well over a pound.
The frame, now divested of all the repair pieces, weighs 1819 g, but the missing piece of TT means it would have weighed ~1850 g originally.
That seems heavy; what do you-all think. My own '86 Davidson, about the same size, weighs 200 g less and it's not the lightest gauge of Prestige. My DT is 3 "notches" from the lightest in fact, and the TT is 2 notches heavier. The rear stays on mine are Col. SL, which should be a tad heavier than 753. Makes me wonder if SBDU subbed in some heavier tubes. I tried a 27.4 seatpost, won't go in even after I spread the pinchbolt ears a little to counter any amount they might be bent in, from tightening on a too-small post. It's my understanding that a real 753 ST should take 27.4.
Anyway, not sure if I want to repair it, still might, but the chainstays are a little gouged up, both sides. I'd hate to put a new front triangle on and repaint it, only to have the rear break soon after. So this might end up being wind chimes or a shop stool.
Mark B